Ah, must be that time of year when we parents are tired of tripping over the holiday gifts!
My son will always help ME pick up the toys, but the change lately is that I'm requiring him to pick up whatever he was playing with before opening up a new bin or leaving the house. This is going so/so. I use the words "respect" and "responsible" a lot when coaching him about what to do. I like Melissa's ideas about giving choices and having him help me, but I'm to the point where I believe that he can do it himself. So begins the training =)
The other day, my son was particularly spirited. He finished his finger paints, and, while I was getting the faucet to a decent temp to wash hands, he proceeded to wipe his fingers over my cabinets. Then he refused to clean up the cabinets and table with the washcloth. I explained that we should respect our things by cleaning up after we have fun, but he wasn't having it, even when I explained that we can only keep stuff that we can take care of. I picked up his paints and threw them away. I REALLY threw them away. It's the only toy that I really followed through with tossing out. He threw a DVD on the floor today when I told him that we wouldn't watch it; I threw it away after reminding him to pick it up. When he saw me throw it away, he fished it out of the trash and put it away. I think that's fine since he knew that was what I ultimately wanted him to do. I congratulate him for being responsible when I feel he's making an earnest effort, and I head in to help finish things up when he's about 50% done. My hope is that he will do it on his own soon.
BTW, the "clean up" song really helps! ("Clean up, clean up, everybody, everywhere! Clean up, clean up, everybody do your share!") Not sure where it's from (Barney? Dora?), I learned it when subbing in a kindergarten classroom. He cues himself to clean up by singing it, and it keeps him cheerful while he's busy putting things away.