Do you know of any other intelligent/interesting/funny cartoon/diagram sites like thisisindexed.com?

http://ubersoft.net is pretty darn good. Its my all time favorite web comic. And, there a plenty of Help Desk archived on there to read through. It kept me busy for a whole semester of study hall.

http://abstrusegoose.com/

I particularly like the comic in which they compare themselves to XKCD.

And the one where they have the door to door science guys.

Cyanide & Happiness

I have a pal who has a site called patentlysilly.com, and it’s all about diagrams of US patents for ridiculous objects. Look in the archives for the fun stuff.