We get rid of all our broken or unwanted racecar parts at Cohens. I'm collecting a pile of crap, old heads, shocks, springs, right now and will probably have enough metal to make a run worthwhile. I usually try to fill the bed of my pickup full to make it worth the trip. Otherwise for just a transmission they may give you a buck or two for it. If you go so far as to seperate the aluminum from the steel then you can recycle the aluminum and get more for it.
When putting my racecar back together after working on it, it's always lighter - for some reason I always have parts leftover on the workbench.