DCImanager - DCImanager is a platform for managing physical equipment. Connect any physical equipment to a single platform. Use the platform to manage your servers, switches, PDU as well as physical and virtual networks.
Stockpile - Stockpile is a free online inventory system for small business and at home uses.
RackTables - Racktables is a nifty and robust solution for datacenter and server room asset management.
Snipe-IT - Managing assets with a Google doc or a shared Excel spreadsheet is more common than you think.
Opendcim - a free, web based Data Center Infrastructure Management application.
inFlow Inventory - inFlow Inventory is inventory management software for small businesses.