Source: *shrug*
What is it: I’ll just cite the tagline: “A Webcomic of romance, sarcasm, math and language”. Very often Randall Munroe simply hits right on the mark with a witty remark, a funny line, or the “alt”-text of the image (Hover your mouse on the comic). He has quite a following, usually totally crazy people. Also check out the “blag” linked on the comic page.
Btw, lately XKCD has been featured on Ehrensenf .
Piled Higher and Deeper
http://www.phdcomics.com/comics.php
Source: Tapestry Comics
What is it: A webcomic about grad students and their work, their problems, their… well.. life. One of my favourite strips that I can really relate to is this one.
http://antwrp.gsfc.nasa.gov/apod/astropix.html
Source: browsing
What is it: “Astronomy Picture of the Day” this page provides you with a high quality image a day to make you think and wonder what’s “out there” as well as explaining what you see in the sky day and night. Images are a great mixture of NASA images (from a whole bunch of sources like e.g. telescopes), images from other official sources and also submissions from people like you and me. To give you some more examples : comet McNaught on Australia Day, ISS on the Horizon, Mars rover Opportunity . Definitely worth a visit.