Oh man, I've been there with the huge bags of toys clean out.
We did one huge overhaul of ds's room around age 3 and ever since, I go in there and weed stuff out about once a month. My Mom likes to buy him all kinds of crap - half of it he rarely plays with ... so we regift it!
Getting his room organized was the best thing i ever did. We have large, clear plastic bins on a shelving unit for all toys. He has a box for cars, one for action heros, one for weapons, etc. Makes clean up so easy and once a bin starts getting "full" - we go through it to see what he might want to give a less fortunate child.
I'm telling you just gifting a few things a week makes a HUGE difference!