Definitely! If I had to pay pet store prices for things I wouldn't have even close to the zoo I have now!
First of all, I generally build my enclosures myself. Aquariums are gotten from garage sales, but lids I make myself. Most of the snakes are either in tupperware (for the young'uns) or in custom built enclosures. A lot of my wood was gotten through dumpster diving or through connections (I demolished our overflow bar last summer and was allowed to keep anything I wanted).
Light bulbs etc. can, as you said, be gotten from a harware store. Fixtures can be bought at hardware stores or, even better, be recovered from garage sales, dumpsters etc. and put to use. The same goes for plumbing, tubing etc. I make my filters myself, too, as all I really use are wet/dry trickle filters.
I got my hemostats off ebay and a lot of the other tools come from the dollar store. Actualy, while I'm on the subject, my local dollar store sells plastic plants as well which is neat for cage decoration. Other cage decorations are taken from the great outdoors and sanitized through baking or bleaching. My snake hooks are golf clubs cut down to size with steel bars bent to shape and expoxied in.
I buy my crickets from the pet store as well as vitamine supplements. I've gotten a few of my animals through the pet stores as well. Other than that, though, I go in mostly to speak to the employees, most of whom I know.