Some primers from those fellas at
Political Betting. The Des Moines Register has Mike Huckabee and Barack Obama leading the polls in Iowa but not by much.
Odds from
VC Bet ~
Result verified by Washington Post
To win the Iowa Caucus (Democrat) - Barack Obama 4/5, Hillary Clinton 6/4 and John Edwards 5/1
To win the Iowa Caucus (Republican) - Mike Huckabee 4/7, Mitt Romney 11/8, Ron Paul 16/1, John McCain 25/1 and Fred Thompson 50/1