I love xkcd too, there are so many great comics there. I printed out the "Compiling" comic and it now adorns by cubicle wall. Another personal favorite is The Difference. I'm surprised the map of online communities was left off your list. I also like the obsessive velociraptor-phobia, it reminds me a lot of Stephen Colbert's feelings towards bears. I also e-mailed my mother-in-law, who teaches math, the Certainty comic. She liked it.

Actually the transcriptions are probably done by readers. Oh No Robot, the comic transcription page, is a project by Ryan North, who writes Dinosaur Comics (and is also the guy behind the hilarious Every Topic In The Universe Except Chickens).