LibriVox is a really neat project that takes volunteer readers who record themselves reading public domain works aloud and packages up the results as completely free audiobooks. This is a great alternative to something like the commercial offerings found at Audible, although it doesn’t have anywhere near the same number of available books to choose from. This is especially true if you stray away from the classics and want something a bit more… modern.
Even still I’ve listened to a few so far and, while some readers are certainly better than others, I have to say I’m quite impressed with the overall quality of the recordings. There are also some mobile apps for iOS and Android that make the whole listening experience very nice.