Check Out:
My Lexicon and
The Cherokee Syllabary
created by Sequoia aka George Guess, and approved by the Cherokee chiefs in 1820.

Other Online Sources
At 101language.com you'll find language courses, a video course in Cherokee basket making and even some PC software to help with learning Cherokee.
Joe LoCicero's, freeware Cherokee Font for IBM and Mac, and a nice pronounciation table. Overall great site.
Here is a computerized Cherokee language tutorial, all done with web pages. Just the basics here, good place to start.
More Cherokee Links

Cherokee Dialects:
Etali
(Eastern) Not as common, NC

Kituwah
(Middle) Western NC

Atali or Overhill
(Western) Oklahoma

Dialect Differences:
The sound ts is sometimes replaced by dl in the Kituwah dialect.
In addition to these syllable changes, some words are completely different due to local language changes.

Places
The Cherokee Heritage Center can be reached at 918-456-6007. They have a museum facility, with village reconstructions (ancient and modern) and a gift shop. They will send a packet of information about genealogical searches if you call them.
Or try the Tsalagi Cultural Center Home Page. They are located in Tahlequah, Oklahoma.
Another locale of interest is Cherokee, NC.

   According to Prentice Robinson, in his Easy to Use Cherokee Dictionary;

The Cherokee language is a branch of the Iroquoian language, as are several other languages. Included in these are the Mohawk, Oneida, Seneca, Cayuga and the one added later the Tuscaroar. To [his] knowledge, none of these tribes can converse with each other in their native tongue. There are related words that are similar in root base.