There are not that many alternatives, but we can still build a list:
GPLI + OCS - this is the most common set up on Debian based distributions. Since you are new to this field I would advise you to start here, counting on its large community.
Pulse 2 - a project by Mandriva that looks very mature with lots of features. In principle also backed by a strong community, but concieved for a different distribution.
Snipe IT - recent, with not that many features, but uses Bootstrap and looks very nice.
FusionInventory - this is an alternative to OCS, meaning that you will still need GPLI to keep a centralised inventory.
Extra: There is a recent GPLI + OCS installation guide at Ubuntu Geek.