And what is the best program to use for that?
Speed (Pitch) and Tempo are two different things. If you are looking for simple pitch change, then the apps that TheLQ mentioned would suffice.
However, if you are looking to timestretch the music, that is change it's tempo without affecting its pitch, then you need something more elaborate.
Ableton Live 8 is my weapon of choice here, but most of the DAWs will do timestretch. You can also get standalone timestretch apps, and there are also VST and AU filters that will do the same. It's a fairly extensive list, just Google "audio timestretch" for some leads.