Zabbix - Track, record, alert and visualize performance and availability of IT resources
inFlow Inventory - inFlow Inventory is inventory management software for small businesses.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
Snipe-IT - Managing assets with a Google doc or a shared Excel spreadsheet is more common than you think.
Prometheus - An open-source systems monitoring and alerting toolkit.
Skyware Inventory - Web-based Inventory Management.