Making the decision to open source your code can be challenging enough without getting into the technicalities of which licence to publish your work under. That's where a site like Choose A License steps in, providing you with an easy way to determine the restrictions under which your code can be used, modified and distributed.
The licences page breaks down a number of popular options, including MIT, Apache and GPL. Each is explained in the form of Required / Permitted / Forbidden, so it's clear what others can and can't do with your work.
One of the noteworthy aspects of the site is that it covers including no licence with your code and what that means in terms of commercial use and distribution. For example, not having a licence doesn't automatically mean it's in the public domain (or under similar arrangement).
It even offers you the option of Creative Commons, if you somehow find yourself looking for a licence that covers content other than source code.