Fun applications of the pigeonhole principle via metafilter.
Drunk Nate Silver, the post-election Twitter meme.
The iPad app Paper makes use of the mathematics of color mixing.
Some Moore’s-law-type extrapolation fun.
Suresh Venkat on the high-dimensional geometry of data mining.
Stan Nikolov’s master’s thesis on detecting twitter trends before they happen.
God plays dice 
The link for “Some Moore’s-law-type extrapolation fun” doesn’t work for me.
Thanks for pointing that out, Igor. I wrote this post from my iPad and apparently ended up at an iPad-optimized version of the article. It’s fixed now.