You can star any Coursera class to receive notifications whenever new sessions are announced.

Also, I believe it's still possible to join the current session (first assignment was due this weekend, but you can turn it in late with just a 20% penalty.)

I take new courses at any time, even if they have ended. Later on, when they recycle, I can do them all over again with ease.

Unless you're attached to getting a certificate of completion, you can pretty much follow the Udacity model. As long as the course hasn't finished, sign up and get around to the videos and assignments when you get to them. There isn't the same discussion forum interchange, and your homework isn't graded, but they don't drop the class from your list even if you do nothing during the run.

Note that you'll want to be careful to cache the materials offline if you do this, especially if you plan on "catching up" after the formal end date for the class. Some of the courses (notably the Princeton algorithms ones) disable access to the materials once the official course ends.

Check out class-central.com for a list of all current and upcoming classes. Coursera also lets you star a specific class and get notified if they are repeated in a new cycle.