This sounds really nice. I've been using apt as a deployment mechanism not unlike the use-cases describe. While the whole thing's been rock solid, the repo management could do with a cleaner interface. Looking forward to giving it a go!
It's grokkable magic :) The Debian package format has nice functionality for deploying software such as the seed database, the script hooks and dependency checking via apt.
Keep in mind it's also possible to run your own apt repositories and have your machines source from those, allowing you to define what specific software runs on your farm, down to the smallest detail.
All in all apt can give you a very flexible setup :)
For nice current images of the Sun, the Proba 2 satellite [1] continuously watches it and dumps some nice imagery/movies. It's ESA sponsored, and both it's sensors (SWAP producing the visuals) are interpreted by the Belgian Royal Observatory. Iirc the Belgians and the Canadians are the only ones keeping a close eye on the sun, counting sun spots and such. Makes for a nice desktop bg also!
Depending on your motives, a fun alternative to the popular Arduino for getting into microcontrollers is just ordering the naked parts and wire them yourself on a breadboard, following Sparkfun's excellent tutorials ("Beginning Embedded Electronics" on http://www.sparkfun.com/commerce/tutorials.php). They start out very basic with building a 5V circuit, connecting an AVR, programming it, adding a crystal and a RS232 level shifter to talk to your serial port, etc, all well explained for beginners. As a software person eager to learn the electronics behind it I've had a lot of fun that way. Great company!
But I didn't mean to detract, that's really a very cool project that you did!