I don't know about software but Akai makes a little box called the (dumb name) "Riff-O-Matic" that plugs into your stereo (or anything that has the common "RCA" plugs) and records 13 or 26 second snatches (the 26 second mode is supposed to have diminished sound quality) of music for playback at 2/3 or 1/3 of the original speed. It also has a feature called the "Note Grabber" that suspends a tone indefinitely, allowing you to find the pitch of that elusive note, as well as a pitch adjuster to step the notes up or down a quarter tone at a time to produce a full tone (I think, may be more) above or below standard tuning. Sells for about $130 U.S dollars but I have seen them on sale for $100.

Sorry for the blatant, commercial plug but I use this device all the time to transcribe complicated or fast riffs. An invaluable tool when trying to learn a particular piece of music, note for note. Otherwise I would never be able to figure it out.

Regards, Neil (now if I could only find a device that actually makes me play better).