4InARow is a slick version of Connect 4 which has been designed specifically for your iPhone or iPodTouch.  You have the option of playing against your friend or the phone and can even set the difficulty level to easy, difficult or hard.

Of all the Connect 4 games out there this is by far the best looking and playing version.  The gameplay is smooth and the computer or human option makes it that much better.  MetaSparc has a winner.