Total Network Inventory: Professional PC audit and network inventory management software - fits best for a for companies of all sizes. Free for 60 days.
Network Inventory Advisor - Network Inventory Advisor audits all network software and hardware simply and efficiently
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
Lansweeper - Lansweeper discovers Windows, Linux and Mac machines in your network.
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.