Craigslist is a big friend of mine. In the past I've been able to find some killer deals on good used stuff and even a ton of new in the box stuff as well. But it takes patience!
Another thing that helps me is to work on little things...things that don't cost too much but take some time to do. For example, I just started working on my engine bay b/c I'm doing some of the typical upgrades (ie. intake, tb, 3G alt, radiator, wp, cam, rr's, etc.) But before I get deep into it I'm trying to clean up my engine bay. So a lot of time moving wires, cleaning, sanding, priming, sanding again, spraying and more spraying. It's not going to cost me a lot besides a lot of time. Check out my progress thread and u can see some little dinky stuff that I like to do haha. Good luck!!!