Here's some links for online sources...
http://www.growersupply.com/sheetpots.html
http://homeharvest.com/containergardenpotsplastic.htm

They are definitely re-usable from year to year. I've put the word out to friends/family so when they buy plants every year they save their containers for me.

I also use a lot of recycled plastic containers from the kitchen (i.e. margarine, sour cream, cottage cheese, etc. Just need to drill a few drainage holes in them first)
I also use a lot of plastic drinking cups this year. Used a soldering iron to poke holes in the bottom. I was able to do 4 cups at a time. This can stink a little so doing it in the garage or outside is a good idea.

Paper pots are also a good option (of course they are not reusable from year to year, but will work well if you are in a bind)

I hope that helps ;)

I save all my breyers yogurt cups and use those.
I never have enough so I also use 3 inch plastic bathroom cups. If the maters get too big for those I transplant to smaller sized styro cups.
I just use a knife for making a slit in the bottoms

I may be too late to help. I just take plastic disposable cups, make several small holes in the bottom and use them.I use a sharp pointed knitting needle to make the holes. Cheap and effective.
Hlily