www.craigslist.org. This is the place for free stuff. I've so far gotten a 75, a 29, tons of fish, including a 10 inch banded leporinus, and plenty of filters and heaters and such. I've also gotten 2 20 gallon and a 55 for free just from asking around to people. Post up an ad on craigslist saying you will take in any unwanted fish/aquariums/supplies, and explain something about your knowledge of fish. It's surprising how many people will give away tanks to the right home.