FWIW, ADW Launcher already has something similar... You can create categories and add apps to these, then switch views from the main launcher to your custom categories (using arrows at the bottom, in the dock), you can even place shortcuts on your home screens that take you directly to any custom category... You also return to your last viewed category whenever you open the app launcher.
If I've confused it, trust that it makes a lot more sense in person. I created a games category, a control panel of sorts for utilities related to phone functionality, and then a miscellaneous category for apps I use occasionally (travel apps, shopping apps, etc.). Check it out, it really simplifies the app drawer.
Using four home screens (mostly filled with widgets) and those four categories, I pretty much never end up hunting around and scrolling for an app.