ComicViewer for Mac

From TildeSoft:

This application lets you quickly and easily view all your favourite webcomics. You can add new webcomics to it quickly, and it includes a helper to assist you in determining the correct search pattern for each comic. The only thing it can not do is view comics that use more than one image in the comic (if people request it, this may show up in a future release). Just open the app, select the comic you want, hit Check Site, relax and read your comic. It's as simple as that.

ComicViewer is also applescriptable. You can tell it to check any known comic from an applescript easily, allowing you to do such things as automatically check all your comics when you log in to your computer in the morning.