If you have Freecycle in your area, list some of it there. In addition to gaining space and organization, you *know* that the person who gets it wants it. The speed in which stuff is taken somehow makes me feel better about getting rid of it - my "no longer needed" and/or "junk" is giving someone else happiness.
I've been amazed at what people want for various reasons - a broken camera lens was in high demand because it contained a small motor that's hard to find. A box of miscellaneous wires and electrical stuff was used in a boy scout project. Sheets that didn't fit our new bed were perfect for someone who had splurged on a lower-end king, but then could only afford one set of sheets. And on and on and on. The other good thing about Freecyle is that you can list one thing at a time as you come upon something you no longer need - there are times it's easier to get rid of stuff that way, rather than making it an emotional 'big deal'. (And it's very common to just leave stuff for Freecycle on a porch, right behind the house, etc - so it's much less creepy/risky than Craigs List can be at times...)
I also make a point to donate to the local women's shelter, and to take DD with me when we go. There's almost always some of her stuff in there - and we take it "to the mom's and kids who aren't as fortunate as we are". I think it's a subtle, but good, lesson for her. As she's through with toys, etc they go into a specific place to be taken there.
Ok - I think I've talked myself into making another sweep here this weekend. Hope it's helped you too .