Here’s a neat AVR based LED clock you can make, all the plans and software are released under the GNU GPL.

It is a clock with a big display unit, that has a DCF77 (german timesignal) Receiver and can be connected to an ethernet network, where it can serve as a NTP server. All of this based on an Atmel AVR microcontroller with 8 KB flash.

NTP DCF77 LED Clock – – Link.