I've been using this plugin for Winamp off and on, and have to say it's slick! In short, it helps make amateurs sound like professional radio jockeys with the crossfading etc.
This isn't a beat-mixing program, but merely a program that helps crossfade one song into another at the right time. The program is called Advance Crossfade (try http://www.sqrsoft.com.ar/ if the link doesn't work, and then navigate from here... or if you'd like me to upload a copy of the file, then post back).
I like the Radio preset but with a small tweak in the settings - turn off the pop ups, and reduce the minimum crossfade amount to 50ms (and not the default 500ms).
Anyone got reviews? I'm all eyes.