There are 1-2 species you might see, and many more that don't make it into our hobby. They can be very tricky, almost always wildcaught and older, as the larger animals tend to be the ones trapped. They have a very short lifespan...about 2 years in a perfect situation (such as hatching them yourself). Tank setups are usually used, but can be hard to keep clean enough to keep the chams from coming down with bacterial infections. As they are so small treating them for much is difficult. There is some species info on these sites:
http://www.adcham.com
http://www.chameleonjournals.com
Kammerflage Kreations has bred them, not sure if they are right now, but check this site for more info:
http://www.calumma.com