I'm still working on getting my kids to clean up their toys. We have days where they do pitch in and help. But, we also have days where they couldn't care less about the toys on the floor. I think they are pretty typical kids in that regard.
I wrote a Suite101 article with a few tips, some that I've found work great and others that I wish I did a better job of enforcing because I think they would work. For instance, I wish I started encouraging my oldest to pick up his toys when he was a toddler. I also wish I never let the amount of toys that we have out in the boys' bedrooms get overwhelming, for me and for them. I'm working on fixing that.
Here is the link to the article.