I use my rpi as an alarm clock. It works well because you have mplayer and cron. And that's basically it. I used picolisp to wire everything together (and wrote a simple hack to snooze the alarm).
But one of the biggest annoyances is that Rpi doesn't have a clock on its own, so when it looses power (I disconnect it), the clock is reset, so the alarm clock won't work.. :(
As I've read "The Unix Programming Environment" lately, I'm quite fond of shell scripts now, and I got to this 4 level quoting that sets the date of my raspberry pi from my laptop.
ssh email@example.com -o ConnectTimeout=60 sudo date --set="\"`date '+%d %b %Y %H:%M:%S'`\""
I'm somewhere between very proud and very ashamed of that, but well... it does the job.