Idea: Instapaper for things to listen to
App for Android, iOS, and Mac
Should enable adding of MP3s, Youtube (lectures), NPR, Podcasts, etc.
You can either choose what to listen to, or be given a playlist of content that will play while you work. I had a similar idea. Could be as simple as a personal rss podcast feed with a bookmarklet that lets you add items. I'd certainly use it. I've created two folders in Instapaper, one called Listen Later and the other Watch Later. It has worked out for the most part. That is kind of what http://dar.fm is trying to do. It would need to sync your location between places....