Tap Tempo is a very simple tool for manually calculating the beats-per-minute of music. With programs like Audacity and WavePad, you can mix music together, but they don't calculate BPM for you, which is awkward.
If you want to know the BPM of a song, simply start it, open Tap Tempo and tap the beat on the space bar. After 10 - 20 taps you'll have an accurate figure for the beats-per-minute.
Tap Tempo is useful if you need BPM, though obviously not if you can't keep time very well! On some Keyboards it's difficult to input a regular beat and while it does calculate tempo, it's a little too basic. It is missing a reset function, and you can only view one calculation at a time. This reviewer has been looking for a tool like this for some time, and despite the lack of features, it does the job.
TapTempo is a very simple app, performing a simple function, but it's only as accurate as you are.