From Shareware Hangvogel:
Determine the tempo or BPM of a song or other piece of music with BpmChecker by manually tapping along with the music, using your pc keyboard. Handy and cool tool for DJ's, composers and other musicians. Features automatic missed beat detection, playing of a music file through your own player and adding the bpm to (and removing from) the played file name or MP3 ID3v2 tag. The played song files are kept in a flexible history list.
Version 3 can add the found BPM to MP3 ID3 tag and play next file in folder.