Here are some of the servers I will be running (note this is for an office of 10 individuals, so we won't be pounding them)... rough ideas on what I'm looking to allocate:
Domain Controller
(1) 30GB Drive
Web Server
(2) 30GB Drives
Database Server
(2) 30GB Drive
(1) 50GB Drive
Exchange Server
(1) 30GB Drive
(1) 50GB Drive