Exchange 2007 OWA
Here is a useful bit of powershell code which I spent ages looking for!
Exchange 2007 turns OWA on by default - which in most schools you wont want for students. Run this (substituting "groupname" for a distribution group for students), and all your student users will no longer have OWA.
get-distributiongroupmember "GROUPNAME" | Set-CASMailbox -OWAEnabled $false
There are similar commands for IMAP, POP3 and ActiveSync - will add those once I find them!
Here are the others (substitute "-OWAEnabled..." or add at the end...)
-ActiveSyncEnabled $True / $false
-MAPIEnabled $True / $false
-PopEnabled $True / $false
-ImapEnabled $True / $false