The calamondin makes the best house plant; and is easy to care for and takes cold pretty well. As for the lemon, in my world there is only the Meyer; all other lemons pale by comparison. Am I biased? Maybe. I have 8,000 Meyer trees and 8,000 more in production for planting Spring of 2012.
The Meyer has the sweetest flowers, is probably the heaviest producer; and the big advantage... on this site are many experts with Meyers in containers; so lots of help.

I'd go with a Meyer for the lemon.

Either of the limes will work and I would choose based on your preference with respect to taste. My Bearss limes tend to droop slightly more than my key limes because the weight tends to be more unevenly distributed but both will do well. The limes will have less issues with ripening than oranges/mandarins.

The orange/mandarins are trickier. We don't have the correct weather patterns growing indoors for part of the season and it can be tricky to get them to ripen fully and bloom at the correct times. Were I choosing for myself I would probably try the navel since I find they are easier to time. With any of these you might find yourself in an alternate bearing situation depending on the indoor/outdoor conditions.

All of these will tend toward bush forms and the habit will be up to you to control. Indoors you will find that you will get some very leggy branches with larger leaves (sometimes 2x the size of normal leaves). Outdoor flushes will look normal. It can be tricky to keep them looking balanced as a result.

Will you be able to control temperature and humidity where the plants will be staying? The temperature will be important for ripening and the humidity will be important if you want to keep lacewings alive (and you should).

Will you have supplemental light or just windows (facing which direction)?

Make sure to avoid peat-based potting mixes. I prefer a version of the gritty mix but you could try CHC or 5-1-1.

Thanks Johnmerr and redshirtcat for your opinions. I'll definately get the Meyer lemon tree.

What's the calamondin orange like flavour-wise? I'm not a sweet fan but prefer tart fruit-like lemons and limes.

I have some options for window placement-ideally, I'd put the trees in the large window of the great room-east-facing also b/c it has high ceilings so could handle some height if the trees grow tall. I could also put them in west-facing windows too. Sadly, no direct south-facing windows that I could place them in front of. What kind of supplemental light would they require? Gro-lights?

I use a humidifier in my home always in the winter so they will not lack for humidity and we have some of the worst humidity in summer here so they'll like that!

The calamondin is known in the Philippines as Kalamonsi; it is picked green and is the primary source of "lemon" for cooking and lemonade; it has a pleasant flavor, but lots of seeds. If the calamondin, which is in truth an orange species, is left on the tree it will turn orange in most climates and it will be sweeter; it makes a very nice ornamental, much as kumquat. I have 2 calamondins and 2 kumquats at my lemon farm; but both are there as garden ornamentals.

Hello there! I know I am a total citrus novice but wanted to add something about how great I think a Meyer lemon tree is. I have killed so many houseplants in the past but by reading up on this site I have managed to keep my potted lemon tree alive for 3 weeks now ( in the wimpy West Virginia sunlight!) I'd say they are a pretty tough tree. :)

P.s. I do have a growlight on during the day while at work.

Ah, so it's in a main area of your house. They will probably survive most winters but with just regular ambient house temps/humidity and no supplemental light I wouldn't try any of the mandarins.

I have no experience with calamondin but I'm sure you would overwinter a Bearss and a Meyer. You'd get better production with a grow light but they are almost all too ugly for finished spaces in the house.

Among the lemons, I have one Eureka tree and one Meyer's. I don't know if it's a general characteristic of Meyer's or if perhaps mine is a dwarf--but their growth characteristic is completely different! The Meyer's is MUCH more robust in terms of horizontal growth, while the Eureka is a strong vertical grower. The fruit of the Meyer's is somewhat more orange and large (which makes sense considering their mixed lemon x orange heritage). Eureka lemons are more yellow and less spherical. I love them both but do believe Meyer's is more free-flowering throughout the year, and I've always felt their flowers were more fragrant. Some people seem to find the Meyer's more temperamental but I have not experienced any differences in ease/difficulty of cultivation. As for the second plant you want, that's a difficult choice. And although they are not on your list, kumquats are probably THE most tolerant of indoor conditions of all citrus and their extended clan (botanically, kumquats have been put into their own genus--Fortunella). They are also very cold tolerant compared to other citrus. The Calamondin Orange (most likely of mixed Orange/kumquat heritage), also is very adaptable to the house and it is more compact--still, it flowers reliably and the flowers are very aromatic. And while you might not want to eat them out of hand (as opposed to a kumquat), they are not without their culinary uses. It's actually one of the secret ingredients in one of my dishes and its favor is quite different than when I have tried to substitute lemon or orange, or even kumquats. Keep in mind though, that in the end, you will not be able to restrict yourself to two trees and might find yourself living in a grove along with many of the rest of us. Happy gardening!

I'm so excited by the rec's for Meyer lemon on this forum. I will probably get one at first, then probably another later.
Still undecided on the 2nd citrus choice-the thornless key-lime might not have very fragrant flowers which is important to me. Some co-workers have bought them and while they are floriforous(sp?)they say the flowers aren't terribly fragrant.
njoasis, johnmerr, the kumquat is a citrus var. that is available to me but I'd written it off as I wasn't crazy about the flavour of it. Maybe I need to consider it and the Calmamondin orange again if the flowers are really fragrant.

Oh, I also remembered, I do have a large, unobsructed south-facing window upstairs where I could put the trees and even install a grow-light, if necessary.

I may be wrong (as it now seems such a LONG time from last spring), but I do believe that Calmondin (in flower) is more aromatic than the kumquat--makes sense again, as Calamondin have an Oranage heritage and Orange blossoms are just incredibly aromatic.

Lily, I agree with Johnmerr about the calamondin. I have a beautiful 3-year old calamondin in a pot that is great looking and easy to take care. No problem at all. I also have a small, 1-year old Meyer lemon from Four Winds that is doing well. It had three lemons on it that I just harvested. Nice little tree too.

Good luck and let us know what you decide.

Jerry

Hi Ladybug:

Just an FYI, the Eureka lemon is generally what is available in grocery stores (the 'common supermarket' variety). Meyers generally are not (unless you have a gourmet type of store).

Happy holidays.

P.

PS I am growing both Meyers and a special form of the Eureka called 'Variegated Pink Eureka Lemon' where the leaves are green and cream and the inside of the lemon is pink rather than lemon. And, along with Meyer's, Four Winds Growers, designates the Pink Eureka as 'A Best Variety for Growing Indoors'.

Here is a link that might be useful: About Pink Lemon Trees

Actually, the common "Eureka" lemon found in the stores could be a Lisbon or Berna (sometimes known as the ELB varieties); or they could be Genova from Chile, Viilafranca from Argentina; or a couple of other minor varieties; they are fungible, that is the consumer cannot or does not differentiate between them and they sall for the same price. The Meyer, where it is available in the same market, typically sells at 2 to 3 times the ELB base price; it is the ultimate gourmet lemon for food, drinks.