Evidence for Relativity:

• Experimental basis of Special Relativity: A superb site.
• Status of Special Relativity: From Wikipedia.
• GPS and Relativity: Relativity in action.

Pages about cranks and crackpots:

• A good article, and just see the the comments...
• From Twisted Physics, and a darn good read.
• Three good rules for crackpots "alternative scientists".
• Are you a quack? Find out here with some excellent questions.
• How to be a crank. Some sage advice.

General sites:

• Bad Astronomy: Discussing and debunking crackpot ideas.
• Bad Physics: Discussing and debunking cranks and charlatans.
• Sense About Science: Countering misinformation about science.
• The Sceptics Dictionary. From Abracadabra to Zombies.

Pages proving Einstein wrong (and each with a different and mutually exclusive reason):

• Einstein Went Wrong: Tedious, but try reading from "As a student at Del Mar High School..."
• The Relativity Challenge: Einstein was wrong and this guy is right. Really.
• Einstein was Wrong: Einstein was wrong and this guy is right. Really.
• Proof Einstein was Wrong: Einstein was wrong and this guy is right. Really.
• Anti-Relativity:  Einstein was wrong and this guy is right. Really.
• The Twins Paradox: Einstein was... Oh you get the idea...

Sites that are either superb spoofs, works of genuine genius, or just plain bonkers:

• The Truth about "E = MC2": Einstein just made it up! Surely this is right.
• The Truth about Relativity: "it is the origins of pie that physicists are analyzing"

Not relativity but worth seeing (from the BBC):

• Skull Quest: "You have to discard the rational mind."
• Senator Sues God: Injunction sought to prevent "death, destruction and terrorisation".