It all depends on how reliable meta’s thread will keep and grow their new user base.
I’m mostly on lovelybooks.de now. It’s a nice community that is not owned by amazon, however it was bought out a couple of years by Hugendubel which is a big book store chain in Germany so it’s not exactly independent.
I’d say, beside the classics that everyone already listed,
But there’s so many to choose from, it’s enough for more than a life time :D
If possible, only convert the wav files to AAC and keep all lossy files as they are.