Slim offered to host a 24/7 server a little while back, but until that gets set up I'm running a temporary server on my laptop. The IP address is 93.96.201.18, enter that into the multiplayer mode for Alpha and you should be able to get in (I believe Alpha is restricted to purchasers at the moment, so you'll need to buy the game if you haven't already). Be warned, there are a number of bugs (such as your inventory/chests/forge being lost on logout) and it won't be up constantly. Also, you can use /iron or /wood if you're running low on resources.