Shapr - A completely free way to build your professional network.
draw.io - Online diagramming application
Event Hunt - Startups and Tech Events Curated By Locals
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
GetReal - Meet new people, in person
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.