Free mathematics textbooks from the American Institute of Mathematics.
The Earth Microbiome Project is a massively collaborative effort to characterize microbial life on earth.
Urban apiculture is a recent phenomenon: instead of raising bees out in farms, amateur beekeepers are raising them in cities.
Now available on public beta: CrossOver on ChromeOS. This should allow Windows software to run on Chromebooks. Whether this will now permit Steam games as well remains to be seen. Regardless, this is really cool.