PlayHex.org is a web application to play Hex online.

Features are:

• play against players, blitz, live or correspondence
• play against bots, at different levels
• request an AI analysis to spot your blunders
• ranked games and rating history

and other features like conditional moves, custom board size and game options, games archive, your account stats, in-game chat…

Play now!

And here is some more links:

Contribute – Contributors – Compute AI moves – AGPL-3.0 license