It seems that when I use the music player widget that comes with the hero, it remembers where I left off in mp3 files! Even after reboot!
So, I use that program to listen to audio books, and any other music player app to play other music. That way I won't have to remember where I was in an audio book. I figured this out by accident, but am so glad I found it because i listen to more audio books than music and I really wanted an app that could do this. Of course I would like bookmarking as well, but still this is good enough.