Feem - Share files offline. No servers. No cloud. No limits.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Winpopup LAN Messenger - Winpopup LAN Messenger is a cost-effective Office, Corporate, Enterprise Instant Messaging solution.
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.
qchat - QChat is a simple crossplatform LAN chat.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services