During my underwater housing project I learned to use and like Atmel micros. Since then, I use them for small devices and controllers. I recently bought an AT90USBkey evaluation board to experiment with self built USB devices.
The small micros, namely the ATtiny 45 may be used with minimal peripheral circuitry and a software based USB stack. This way it is easy to build simple USB devices. My camera controller device CamControl is a project where I used this approach.
There's also a sample how to enhance a fashionable accessory (a bow-tie) with a micro. In cooperation with Martin Mascherl, I built a prototype of an illuminated bow-tie.
With only an ATtiny 45, four resistors and four LEDs I built a circuitry that mimics glowing amber and the flicker of burning flames. The bow-tie is made of transparent epoxy and colored glass beads. The micro is connected with an ISP socket to the outside world. This way it may be completely re-programmed any time after production This allows me to fine-tune the light effects.
One of my recently acquired devices runs the .net MicroFramework. It features an Ethernet stack and allows to build devices that are controlled via a network connection.
Microsoft provides a sensor API for Windows 7. I've got a device with a few sensors. I've experimented with it on my PC running Windows 7. There are quite a few funny things one can do with real world data on a PC.