TechEvents.co - Tech and startup events aggregator

Konflist - Curated list of tech conferences all around the world!

Event Hunt - Startups and Tech Events Curated By Locals

Calendify - Calendify is an event community where you can share, publish, and subscribe to event calendars. It helps you to stay informed about what you are interested in and what is yet to come.

Shapr - A completely free way to build your professional network.

Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.