The "Tea Party" is just a loose coalition of people who are dissatisfied with the Federal government. They really aren't united on any political philosophy or ideology, and it isn't a political party of any sort.
It's inspired by the "Boston Tea Party" revolt by the colonists against the British (
http://en.wikipedia.org/wiki/Boston_tea_party) about two years before the breakout of the American Revolutionary War. Albiet instead of muskets and running for the hills, it's protesting and holding up signs.
http://en.wikipedia.org/wiki/Tea_Party_movement
Also, here's some older threads related to the topic:
http://dis.4chan.org/read/newpol/1268236648 - Tea party movement
http://dis.4chan.org/read/newpol/1239845767 - Would you like some tea