Feeling ambitious in the hack department? Try taking on the DIY Pong Clock.
"Hardware hacker Ladyada has released an open source retro arcade style table tennis for two clock called the MONOCHRON. According to MONCHRON project page they 'wanted to make a clock that was ultra-hackable, from adding a separate battery-backed RTC to designing the enclosure so you could program the clock once its assembled.' It includes a ATmega328 processor (with'Arduino' stk500 bootloader for easy hacking). It's completely open source hardware, all firmware, layout and CAD files are yours to mess with."