Picking Up Toys

Obviously I want my kids to pick up their toys out of their utmost respect for my authority :), but I also want them to have a good attitude about their work and here are a few ways we deal with the issue of picking up toys.

1. I like to say (and I mean this), "I like to help hard working kids." - so long as they aren't slacking (and I don't have something else pressing) I'm happy to help out.
2. Caleb gets a kick out of racing the timer, we've found we can clean their room in about 5 minutes if everyone tries to beat the timer. (This has also helped Caleb understand how long 5 minutes is, he'll want to know how long something is and I can say, "as long as it takes to clean your room...twice")
3. Sorting - I have no idea why kids need to learn sorting at school - Annalise has no trouble sorting toys that belong in a set from toys that belong in a general toy box. When their room really gets messy, I will push everything to the center in a heap and assign toy types (ex. Caleb picks out blocks, while Annailse finds all the Little People)
4. The Age Game - Annalise has to pick up 2 toys because she's 2 and Caleb has to get 5 because he's 5, repeat until everything's picked up - I sit back and relax with this one!
5. One-on-One - Caleb is actually has started feeling proud of a job well done, so he gets a better attitude as the room gets cleaner, but Annalise has a hard time staying focused, so sometimes I will tell her individual toys to pick up.

That's pretty much my arsenal right now, do you have any helpful ideas for encouraging kids to have a good attitude while picking up their toys? I *like* the idea of having them play with one thing and putting it away before playing with something else, BUT I really like to see how they fit multiple sets of toys together too.