Not sure what the "best" card is (probably varies from person to person) but I think this card is good as a primary card for random purchases:
http://www.firstusa.com/cgi-bin/webcgi/w...CLUKRKQCnjV8IIQ
0% APR for 12 months and 1% back on purchases. There are probably a lot of cards out there with more rewards, but I'm not aware of any that also have 0% APR. In some sense I think the 0% APR is more important because you are essentially getting up to 5% back (in the savings account interest that you are not forgoing) on your purchases. Of course that effect is greater on the earlier purchases, but I still think it probably adds up to more for most people.
If you do some research there are tons of cards that are good for particular purchases or good for specific types of rewards like hotels. Fatwallet has a lot of good advice on stuff like that.