Really good article here:
http://www.itquibbles.com/sql-sbsmonitoring-high-disk-usage/
Solves the problem of the database reaching max capacity, and also speeds things up in general.
Short version:
In SBS 2008, run the contents of this zip file in an administrative PowerShell window.
In SBS 2011, start this shell as administrator:
C:\Program Files\Windows Small Business Server\Bin\MoveDataPowerShellHost.exe
and then while in the shell, run the contents of this zip file.
If it says “1 row affected”, it’s done, and the messages will point out old MDF and LDF files to remove.
You may notice that the script linked here is just a tad different than the one on the itquibbles page; this one just adds the -force items mentioned as an option on that page.