All of the above, plus media -- interviews and b-roll for documentaries and news programs and DVD extras and such that need to be transcribed so that they can be edited into something usable, which is where most of my experience has been in. Media transcription I have found to be often often educational and/or entertaining, although it is equally often mind-numbingly frustrating and dull. For a more entertaining description of the variety of freelance transcription work available, I recommend this article.

I got used to using a transcription foot pedal at my in-office job, so when I switched to freelancing at home, I purchased my own. The foot pedal lets you play, pause and rewind a file without having to move your fingers from the keyboard, and therefore speeds me up considerably. But there's also free software that lets you do similar things with keyboard shortcuts, I just find the foot pedal a lot easier.

I will get back to you on the textbook indexing!