I use PIC micro's (sort of the same). A few projects I have done:
-Wireless thermometer using Bluetooth
-Wireless Datalogger using Bluetooth
-SPI LED controller (uses WS2801 LED RGB led controller)
-LiFePO4 Battery controller (something is up with the firmware that I cant find so I just rely on checking the battery once in a while)
-Conceived a Power monitor for the house (haven't implemented it-its only theory)
-Conceived much of the same system as Chuck for controlling a stepper, just different software.
-Played around with the idea of making a motion sensitive sound playing thingy mabob (Highly technical wording right here)
-Various other ideas that didnt make it because of time, and cost. Most of the them are simple enough a 555 timer can be used, or there is specialized hardware (ie LED controller)
These are just some ideas. Check around
http://hackaday.com/ for some more interesting stuff. Make magazine also has arduino heavy stuff (
http://makezine.com/volume/make-42/).
I also have 32 Bit and 16 bit Microcontrollers just sitting around. Ive played with the 32 bit one, but its a whole different ball game, I have to learn a whole different programming language and register usage to use them. Speaking of registers, if you do get inspired, Read the data sheet for your micro. It may take a few readings, so print them out, sit down and enjoy a hot beverage (or Cold beer). Make/take notes. I know Microchip does a pretty good job at showing what register does what, and they often give source code. Most of the time I print out source code I find on the web, and also print out the page from the data sheet that goes with it, and go line by line to understand what it happening. I have a personal angst against arduino that its users are spoon fed info and assume its correct, and sometimes its not!