Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Event Hunt - Startups and Tech Events Curated By Locals
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.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Prometheus - An open-source systems monitoring and alerting toolkit.