I would think the contractor may be not the electrician, if you have one, would provide the "cans" although you will probably pay for them one way or another.

Although, I was stunned when my contractor told me yesterday I needed to buy the wall receptacles, you know the plugs in and switches, so it doesn't surprise.

Our electrician provided everything in and behind the wall like cans, undercab lights, switches, trims and even bulbs for the cans. We provided any hanging fixtures. It was all spelled out in the bid. We went through every decision together if color or sizes were involved. I think most electricians prefer to buy their own supplies since they purchase through a regular electrical supply house and can be assured of the quality of components that are used.

Thanks. I don't mind being billed for it - I just don't want to shop for such a mundane item, let alone one which I know nothing about :P

You wouldn't believe how many choices there are - check out any of the major manufacturer's websites or catalogs (i.e. Progress, Lightolier). There are 3", 4", 5", 6", screw-base bulbs, CFLs, LEDs. The "trim" - the part you see when installed - is often sold separately from the hidden lamp-fixture hardware. The latter can be standard, insulated-ceiling, remodeler, shallow spaces, etc. The trim can be a white or black step baffle (the most common), a silver or goldtone Alzak cone (parabolic reflector that allows use of standard, non-floodlamp bulbs), and all sorts of glass or plastic diffusers. There are cheap contractor cans, standard cans, high-end "architectual" cans.

Click on this link and then click on "Show All Results" to see one manufacturer's options, all 249 of them. Then click on this link, and again on "Show All Results", to see the 60 different kinds of underlying recessed housings they make. If you let your contractor choose your recessed cans, it's a crapshoot as to what you'll get.

I agree with lee676. Recessed lighting was an area I did not understand that there were so many choices. Once I did some research on the subject I would have selected Juno and the Alzak Wheat Haze trim rings. I was too late and the electrician installed Halo. So I have 5" with Alzak (silverish) trim rings.
Also, I purchased (by choice) my switches/outlets/covers, etc as I wanted to select the color and style

I went & bought the 5" and 4" halo cans at Lowe's, then later bought the Alzak trims online. The electrician would have killed me on the price had I bought from him. I pinched some pennies.
Casey

I'm about to start a complete reovation of my kitchen. My contractor will be supplying all of the electric fixtures. I asked him if I could supply the 3" recessed cans as I found them online at an incredible price. He said that he couldn't buy them from his supply house for the price I was paying and asked for the name of the company. You'll find a link below.

Here is a link that might be useful: Contractor Lighting

Usually the electrician will supply the cans and trim, but you can also work it out ahead of time with your electrician if you want to purchase the materials. As others have pointed out, you have some decision-making to do! What size cans will you have--4", 5", 6"? What color trim? White baffles are pretty standard and inexpensive. I don't like black baffles because they look like black holes in your ceiling, though they do reduce glare. If you want to go fancier, the Juno Alzak trim reduces glare and looks slick. Juno Alzak comes in several colors, but the most popular are Clear or the Wheat Haze.

We bought our own cans and trim. We chose Juno 5'' IC Remodel Housing #IC20R, and bought them at Sears online for a good price (look for Sears coupons online--we got an additional $5 off, and hey, every dollar helps).

We also chose Juno Alzak trim in Wheat Haze, which we bought at electricsuppliesonline.com, though it was a couple of weeks of a backorder wait. One of the threads that helped me was "Put Me out of My Misery and Just and Tell Me What Kind of Cans". Though your head may be swimming after reading it, and in that case, it may be easier just to leave it to your electrician to purchase everything.

If you don't mind doing a little research and if your electrician is cool with it you can save quite a bit by getting lighting materials online. The first electrician I got a quote from wanted to provide materials and they were not exactly what I wanted plus he wanted an arm and a leg for them.

The electrician I went with had no problem with me providing the materials. For many of the materials the difference between online prices and local retailers is huge.

The cans I decided to use were cheap Halo 6" cans. I ended up buying them from Lowes as there was no significant savings to be found online. However, the Cree LR6 LED fixtures I put in them were $78 each from an online retailer which was a big savings over anything local.

For under/over cabinet lighting I bought CL2 low voltage wire online and he installed it. Good wire is incredibly cheap online and incredibly expensive locally.

I also bought the transformer and led light strips online. He installed the transformer. I installed the strips which consisted of screwing in a few little clips and plugging them in. Again, big savings - especially if you know where to get the LED strips from.

He wired boxes for my island pendants. I got the 12V fixtures online and hung them myself. Again, pretty easy to install.

I ended up with nicer and more efficient materials at a much lower cost than I was first quoted.

Paying an electrician's wages to order and fetch cans is expensive.

I am sure he will not mind making the extra money though.