two L293 or L298 h-bridge ICs seems fairly cheap at e-bay,
Does anybody know of a good and cheap source for multiwatt-15 heatsinks?
Also - you might want to buy one or two L293 or L298 h-bridge ICs (note that the L298 can -not- be plugged into a breadboard or perfboard as-is - but it does have a higher current rating than the L293 and can be bridged as well - there are people and places online that sell adaptor PCBs). Once again (and especially with these parts, as they can eat into your budget) only buy these if you think you will be doing projects with DC motors (and even then, you might want to wait); I don't consider them expensive parts, but I don't know your budget, either.
The motors are rated 4.5V-6V with a no load current of 250mA and a stall current of 1.8A @ 4.5V each.
Finally - you might want to think about (and perhaps purchase) something for storage of your parts. I always reccommend Stack-On multi-drawer bins, but they are fairly expensive, and you need the room for them, and they may not be ideal for your "workbench".