Sources of Intelligent Audio for Commute?

confusus writes "Trapped in the daily routine of commuting for 1-2 hours every day, I started to ponder different ways of recycling commute-time waste. I tried listening to the radio, but 9.9/10, it ends up being just 'duh-whatever.' Then, I tried listening to audio books: it is really hard to find audio books that are tailored toward nerds. Thus I decided to find audio of interesting/geeky/nerdy/sciency interviews, talks, lectures. What would be the websites which provide such content?" I'd really like to find more informative downloadable audio content, too. Perhaps informed commentary and self-guided tours of historical and other sites, like national parks and significant buildings in the U.S. and elsewhere, basically self-guided audio walking (or driving) tours. Can anyone recommend a source?