My googling is failing me. Here's what I've got so far:
According to a CBS poll: "According to the poll, 95 percent are white, they are just as likely as Americans overall to have college educations and to make over $50,000 a year."
via Cuumbaya, a CNN poll seems to say (on page 5) they're 80% white, 2% African American, and 10% Latino, but if I'm reading that right, what're the remaining 8%?
ETA: via medievalist, a later New York Times/CBS News Poll: National Survey of Tea Party Supporters gives 89% white, 1% black, 1% Asian, 6% other, and 3% refused.
ETA 2, via serialbabbler, from Tea Partiers Are Fairly Mainstream in Their Demographics: