If your phone, mp3 player, or whatever else you use can't speed up podcasts/audiobooks enough, or it only does that while increasing the pitch, just use this utility.
It copies over important ID3v2 tags, so the files should generally be tagged correctly.
It works on Linux and OSX, you need sox and id3v2 programs installed first.
speedup_mp3 -1.4 file_in.mp3 file_out.mp3
speedup_mp3 -1.5 directory_in directory_out (directory_out must exist first)