If you don't already know, for my final year project at university I'm making a massively multiplayer game, called Rawkets, that utilises HTML5 canvas and WebSockets. Right now it's in a very early stage of development, although it has already proven quite addictive for some people.
In short, the finished game will be something like the HTML5 offspring of Eve Online and Facebook. To be honest I've never played Eve Online, but more than one person has compared Rawkets to it. I like to think of it as a social network in space.
The general concept of the game is that each player will have a rocket and a planet. The rocket is their mode of transport, which allows them to visit other players and planets, and the planet is their "home-world", which is like a social network profile that stores information about the player. The idea is that players will gain experience points by accomplishing various tasks within the game, like mastering the rocket controls, making alliances with 5 players, staking your flag in an empty planet, visiting a player's planet and leaving a message, etc.
As you can tell the game is still in the early stages of development. I have 6 months left to work on it and I'm sure all will become clear during that time. Have faith.
For now, enjoy these two videos of the game as it stands with basically none of the features I mentioned above, apart from rockets. You can play the game as it stands on the development server, although I can't guarantee it will be online 24/7. I've also open sourced the code so you can watch the development line by line.
I nearly forgot. Make sure to follow @rawkets on Twitter for announcements and opportunities to test new features.