4 alternate high quality logos for the wolfram alpha search engine. (2 with reflection, 2 without)

Blog of string-theory skeptic Peter Woit. String theorists hate this guy, especially Luboš Motl, whose blog The Reference Frame I also submitted a logo for.

An opaque, nearly all-black logo.

This is the logo of arxiv.org, the most important database of physics and mathematics eprints. I made the smiley so that it resembles the original logo of that website.

EDIT
Looks a whole lot better.
xkcd is "A webcomic of romance,
sarcasm, math, and language."

"Warning: this comic occasionally contains strong language (which may be unsuitable for children), unusual humor (which may be unsuitable for adults), and advanced mathematics (which may be unsuitable for liberal-arts majors)."

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xkcd - A webcomic of romance, sarcasm, math and language.
Ingenious humor by Randall Munroe.