A gross oversimplification: Scrum has project management techniques for any kind of project, and can be applied outside the software world. XP is focused on building software with a few bits of project management. The parts of XP that overlap with Scrum are compatible enough that they go well together.
FDD, XP, Crystal, RUP, and so on each have similar but different recipes for how to run projects and write software. They're close enough that the inventors and people dedicated to each one are on good terms. See AgileAlliance.org for some of the commonalities. I think you'll have to Google for references, books, articles, etc. and make your own list of what's the same and different. Be careful in your reading ... some people who don't like one method or another make up horrible things to dislike that aren't in the real methods at all!
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi
The book "Agile Software Development Ecosystems" has a nice overview of the different Agile Approaches (I hesitate to call them "processes").
If you don't want to read a whole book, it would probably help if you asked some more specific questions; or tell us why you are interested...
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus