Steven Pinker discusses the interplay of language and the mind and how psychological processes have shaped the English language.
The best stuff is about using Google’s enormous database of word-from-books to track how language evolves over time, in particular the gradual erosion of irregular forms in English (keep/kept and drive/drove) in favour of their regular counterparts (beep/beeped and jive/jived).
Which you WILL want to follow up with a visit to Google Ngrams - http://ngrams.googlelabs.com/ - essentially Google Trends but with all written words in the English language for the last 1,000 years (instead of all search terms in the last ten years).
Mind-blowing.