Some helpful audiobook resources

Ambling BookPlayer - free (or paid upgrade) app available for Android, iPhone, iTouch, and iPad. The online library can be organized by free and paid. The audiobook downloads straight to your device. However, these are big files and unless you have an unlimited data plan, you should download via a wifi connection.
Librivox - free, volunteer-recorded audiobooks. Downsides - the catalog is difficult to navigate, some of the readers are less skilled than others. On the plus side - free public domain audiobooks, multiple recorded versions, multiple languages.
Audible - Amazon-owned premium audiobooks. Downsides - these get pretty expensive. Upsides - they offer an extensive library and quality recordings.
OverDrive/Media on Demand - this free  service lets you borrow audiobooks electronically straight to your mp3 player, smart phone, e-reader, computer, or alternatively, you can burn them to cds. Though, if you're going to go through the effort of burning all those CDs, you might as well just go to the library. While the wait is impossibly long to borrow e-books, significantly less people listen to audiobooks. The search feature isn't very accurate (and the selection includes a lot more popular and genre fiction than literature), but I'm sure these pitfalls will be improved in time. To see if your library is participating in this service (or something similar), visit your library's homepage.
Your neighborhood library - many libraries have a moderate selection of audiobooks on CD and cassette, in addition to offering mp3 downloads online. Also, a lot of libraries will borrow an item you requested from another library to lend it to you. In my experience, not many people check out audiobooks on CD regularly. At least, at the library I frequent, the selection the audiobook section is always full of CDs and empty of people.

Know any other resources that might be helpful to audiobook readers? Let me know!