Don't drop the clay.

[SpeedingFirebird]

You can buy Meguiar's Quik Clay online:
Quik Clay Detailing System
G-1116 16 oz. (473 ml) $9.99

at http://www.meguiars.com/store_meguiars/index.cfm

Stuff works awesome. At the risk of sounding like a commercial. I use all Mequiar's products because it was recommended by a friend that repairs exotic cars. Paint cleaner, polish, wax, etc.

[Camarorulz]

If you're using a clay bar long enough to make it fall apart you've used it WAY too much. A good way to preserve clay is to tear the big bar into 4 pieces, put each piece in a plastic bag, and use them on different occasions. That way you get 4 uses instead of the max of two on the one bar.

[Crashtest]

O.K., for everyone that uses a clay bar. Please, & I say Please, put newspaper under the spot you are cleaning. Just an FYI, LOL

[meissenation]

Unfortunately clay bar is the same no matter what brand or company it's from, it's all the same exact part number.

[Jonas]

I found some clay bars only on ebay

Clay bars