Generally, yes. Most onboard graphics support one or two monitors. Most recent onboard graphics can be used even with a discrete card or cards installed. Max monitors = max for iGP plus max for cards.
Behemoth - Plex server
Galactica - FreeNAS
Pegasus - R710 ESX host
fsociety - MBP 15
Rocinante - E5530 testing machine
Saratoga, Ticonderoga, BunkerHill - the Hydra desktop PC-thing.