Chip,
click on the sportsbooks tab up top and then on "perks/bonuses".
20% would be pretty solid, be careful with a book that may offer more.
Of the sponsors up top, I would recommend BetJamaica if you are looking just to bet the major sports.
For more exotic offerings, 5dimes and Bookmaker are solid.
All three offer 20% bonus and will cover fees.
More importantly, all three will pay you.