There are several good telephoto lenses (the kind you want to buy) available for your cameras. Since your current lens can cover distances to 80mm, you should look for one with a focal length of at least that. Bigger numbers indicate the ability to handle longer distances. A 160mm lens will focus to twice the distance your current lens will. A 240mm lens will focus to three times the distance. However, as this focal length increases, three things will happen to the lens: it will get more expensive; generally larger and heavier; and less able to handle lower levels of light. Expensive is expensive; there is not much you can do with that besides buy a used lens or a third-party lens (in your case, a lens by anyone other than Canon). The inability to handle lower levels of light can be compensated for several ways. You could keep the camera lens open longer to admit more light -- but that can cause blurring if you're shooting a moving subject or holding the camera without a tripod. You could use flash, though the flash that comes on the camera likely won't have enough power to light something far away, so you might have to buy a flash unit. You could spend more money :-) and get a telephoto lens that has a wider maximum aperture. These are sometimes dramatically bigger and heavier than less-capable lenses. Or you could buy an "IS" (Image Stabilization) lens; the lens largely eliminating blur caused by handholding. Neat feature; not cheap. If you choose to buy a used lens, it's best to buy one in person at a place that sells used photographic equipment and will give you at least a little warranty. Bring your digital so you can see some results right away. Since Canon is a popular brand, if you live near an urban area you shouldn't have trouble finding a good lens. If you buy a third-party lens, stick with better-known brands (Tamron and Tokina come to mind, but try to avoid their very cheapest lenses). A good third-party lens will have a metal lens mount and operate smoothly and quietly. You also will have to make sure it works with your particular Canon camera model. Sometimes third-party lenses don't work well with a given manufacturer's camera, so you may lose some automatic features or exposure information. That's a lot to digest at once, I'm sure. There also are several Web sites which discuss lenses for Canons -- but be warned that there is just a firehose of information out there because Canon is such a popular brand.

You are absolutely correct that learning how to manipulate the shutter speed and aperture to maintain the desired depth of field is the finer points of photography, but with the advent of auto focus and auto exposure controls that is rapidly becoming a lost art. Back in the mid 60's when I learned photography we all we had at best was manual focus and stop down match needle metering. Try shooting action shots at a football game when you have to manually focus and compute the exposure for each shot and you will rapidly find out the action is long gone before you even get a shot off. Add to that, we were working with fixed focal length prime lenses. The solution was to go to the sidelines at mid field (50yd line) and select a lens focal length that would give you closeups at mid field or at either end of the field, typically a 200mm. on the lens barrel you will see a center line that indicates the distance from the camera to the subject. On either side of that index you will see small lines that have an f-stop index number, one on each side of the center focus index. That is the depth of field scale index lines. The smaller the aperture the wider the distance between the index lines, and the greater the depth of field. Rather than focus the lens on a set point, rotate the lens until the infinity mark is on a depth of field index on one side and look at the corresponding depth of field mark on the opposite side to see what the closest focal point is. By example, a 200mm lens at f-16 has a maximum depth of field of 24' to infinity. A 300mm lens at f-16 would give you a depth of field range of 90' to infinity. The ISO or film speed index is equal to the shutter speed at noon daylight at the equator. As we move north or south of the equator the light falls off. On average, at noon in the USA the ISO number is equal to the correct shutter speed with the aperture set at f-11. We need a minimum shutter speed of 250 and f-16 is one f-stop slower than f-11, so we would use ISO 400 film (slightly less than one f-stop faster). With the modern digital cameras offering shutter speeds up to 1600 or 3200 it is much easier. Set the aperture at f-16 and set the ISO at 800 and you could shoot the whole game without making another setting on the camera.

Although I am currently only working as an advanced amateur shooting for my own purposes, way back in the late 60's while in the Air Force I was professionally trained as a "Still Photographic Specialist" and I worked as a professional photographer for a short time after I got out of the Air Force in 1972. I principally shoot Pentax invented the through the lens pentaprism viewfinder and they were the first company to make cameras with a built in light meter. At the time Nikon was makng the Nikon F, which is unquestionably one of the finest camera ever made, but the Nikon F did not have a built in light meter, Instead they had an optional viewfinder that had the light meter built into the viewfinder and with the optional viewfinder it was designated the Nikon F Photomic. Canon was still making some world class rangefinder cameas but they had not yet got into the SLR market. From 1966 until 2006 I had amassed a collection of 21 ranging from an 16mm fisheye to a full 1,000mm that weighs in at nearly 32lbs including the dedicated wooden tripod that came with it. Pentax lenses, so when I decided to upgrade to Digital I chose a Pentax camera because Pentax has reverse engineered their digitals so we can still use all of our lenses. Needless to say, I am fully comfortable with a totally manual camera, although I do appreciate the conveniences of modern technology. As a sideline, I have been teaching a free photography class at our local senior center for about a year, and as you might imagine I hear your question quite often. First off, let me make it perfectly clear. Just buying a professional camera will no more make you a better photographer than what buying a stethoscope would make you a nurse. Before you buy a camera you have to stop and think about what you intend to do with it. If all you need is a camera to take good high quality scenics and family album type photos then I would not recommend the expense of a true DSLR. Professoinal photographers need a DSLR because they need to select lenses for the type of photography they perform. By example, a news photographer needs a fast normal lens and generally a moderately long telephoto, whereas a sports or wildlife photographer needs super long telephoto lenses while a scenic photographer needs super wide angle and a portrait or fashion photographer needs normal and short tele lenses and a nature or forensic photographer would need macro lenses for super closeups, while a laboratory photographer might need a microscope adapter for their camera. While that Nikon D3100 package is a very good deal, you must keep in mind that it is an entry level DSLR and while it does have enough automation that you can basically take it out of the box and use it as a point & shoot while your learning, but if you decide to really get into serious photography within a year or so you will begin to see its limitations. Basically that camera has different modes, which means you can select Full Automatic mode, Portrait Mode, Scenic Mode, Sports mode, etcetera and the camera will make the necessary adjustments to meet the need of the mode selected. It should also have a manual mode so as you advance it will work with you. For a true beginner making the initial switch from basic Point & shoot to a more sophisticated camera I would advise you to consider what the industry now calls a "Bridge Camera". (In fact, I bought a bridge camera as a backup camera). Generally the bridge cameras have the same basic shape and size as a DSLR and many of the advanced control features but instead of interchangable lenses they have a super zoom lens and they cost much less. By example, Walmart carries a number of bridge cameras from Nikon, Canon, Fugi and Kodak. My personal choice was the Kodak Easyshare z981, which has 14mp resolution and a 26x zoom lens(equivalent to a 26 to 676mm zoom.) It has a 3" display on the back of the body and it will shot both stills and video,and it has all the modes that you will have on that Nikon. All for a mere $238 plus you will have to buy a memory card separately. Another great bridge camera is the Canon Powershot SX30-IS. It has a 35x optical zoom and sells for $350. One word of caution. 200 to 250mm is about the longest lens that you can successfully use as a hand held camera. I would strongly suggest if you buy a camera that exceeds 200mm or 8x you will need a tripod too. Having said all of that, no matter what camera you choose, in the beginning you will feel a bit awkward until you get the feel of it. If you run into situations you don't understand or you have photos that you would like constructive criticism I would invite you to post them in the photography forum and their are a number of very knowledgable ppl that will help you along as you learn.

What's your budget, what sports are you trying to capture? What's your "qulity" expectation? I think we need more info on your needs. Here is a link that might be useful: Savannah Photographer