I've always liked the idea of workboxes. We're pretty laid back here though, and it seemed maybe a little too structured for us, so I've never really pursued it.
Recently though, I've realized we needed something a little different around here. L is constantly asking me how many more things we have to do for school, which sort of drives me nuts. I've also realized that although we get through our official lesson plans on a daily basis, we haven't been getting around to doing some of the fun "extras," (things like games and puzzles.)
I recently picked up this toy organizer at a neighbor's garage sale for eight bucks. (It's a slightly smaller version of the ones Target sells for around $30.) We've started using it for our "workboxes," and it's been really helpful for us in several ways.
I load the next days "work" in the box at night. On an given day, our lesson plans might include 5 or 6 different activities. (Remember, we're using Heart of Dakota curriculum, but I am tweaking it slightly.) In the empty, leftover boxes, I include "fun" stuff, which may or may not be related to the loose theme we're working on.
For instance, right now, we've been learning about "Halloween stuff," which is a pretty broad topic. Some days the empty boxes might include Magic School Bus movies about bats or spiders, Halloween bingo, or candy corn math activities.
Some days the extra boxes are full of activities that don't necessarily fit our topic, but are educational in some way, like board or card games, art assignments, etc.
L can now see what is expected of him, and I think he enjoys being able to see that we'll be doing a mix of "hard stuff," and "fun stuff."
I'm also doing a better job of including "extras" on a day to day basis. All the fun stuff I've been collecting isn't just sitting around collecting dust in the cabinet anymore.
We're using this system pretty informally, but it's working wonders for us.