Usability 
View your favorite daily comics in your mobile browser with Stripr. You can customize your Stripr by choosing from over 150 different strips including geek classics like xkcd, Dilbert and Apple Geeks as well as some mainstream comics and some really obscure ones. The comics are pulled from user submitted RSS feeds and not all of them work. Check the user ratings which are a good guide to which ones are functional.
Billed as an iPhone webapp, Stripr also works well with the Android browser and Opera Mini. You do have to register to use Stripr but registration is free and only requires an email address.
12-Jul-2013: Very few of the comics links on Stripr work any more. One that does is xkcd