I’d really love the ability to have an RSS feed turned into a podcast automatically. I don’t think it would be that hard to build a site where people could put in the URL of an RSS feed, and in return you’d give them a URL for an audio-version of that feed, where you’d use a text-to-speech library to convert that content to audio.
There are a lot of times I’m walking and would like to catch up on specific blogs. Also, being the motion sick type, if I’m in a car or bus it would be great to be able to “read” without the discomfort of taking my eyes off the surroundings. Someone get on it!