Here's one site on Wikipedia:
http://en.wikipedia.org/wiki/Sorbs***
I might advise you not to take too seriously the various names of the various ethnic groups: I know that Wend/Venetii and Sorb/Serbian are obviously related words, but so are the Germanic ethnic terms Swabian and Swede (both from proto-Germanic *swebdi), while today's Swabians and Swedes are certainly two very different peoples.
God bless you!