Top eLearning Web Applications, like Dokeos and Moodle, you can download for free
This is a presentation of 10 open source web systems for eLearning.
You can use them in universities or other educational organisations to have teachers and students co-operate online.
From what I saw Dokeos and Moodle are perhaps the best choices, but this depends also to particular needs one may have.
If you start with an eLearning platform you’ll have to go on with that, so be careful in your final choice and you’d better try 2 or 3 before you decide.
Almost all applications require PHP.