It partly depends on what you want - hotel or airfare or flexible points. In additon to those mentioned above look at:
Southwest Airlines. I believe the current offer is 50,000 points. Fee is not waiver the first year.
IHG (includes Holiday Inns and Crowne Plazas). Offers are generally in the 50,000 to 60,000 range.
After the first year, annual fee is $49 but you get a free reward night.
Hilton (includes Embassy Suites and Doubletree). Current offer is 75,000 points (higher than usual). No annual fee.
I think each of these has a spend of around $2,000 within 3 months. I was too lazy to double check the particulars, these are based on memory.