Boost your brain
This Popular Science article tells how to increase your brain power. A lot of it is specific to science, but there's enough general information to make it a worthwhile read. (Warning: Taking the scientific assessment on page 2 could be damaging to your self-image. I scraped by with 4 correct out of 13 and consider myself lucky.)
If you're looking for more brain exercises, check out MyBrainTrainer.com, which bills itself as the world's first virtual mental gymnasium. The site requires subscription, but there is a free one-week trial available.