GLPI - GLPI is the Information Resource-Manager with an additional Administration- Interface.
inFlow Inventory - inFlow Inventory is inventory management software for small businesses.
Lansweeper - Lansweeper discovers Windows, Linux and Mac machines in your network.
Snipe-IT - Managing assets with a Google doc or a shared Excel spreadsheet is more common than you think.
FusionInventory - Fork of the OCS Inventory project that enables users to inventory their IT assets.
Skyware Inventory - Web-based Inventory Management.