I found that my Mini becomes unstable and sometimes freezes if I leave my SMB shares mounted for days at a time. So, I combined several scripts found on this site into a new script that unmouns all volumes when the computer's been idle for a while.
The main credit for this goes to this older hint.
[robg adds: I haven't tested this one...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=2005072112123393