iTunes: auto ramping up/down to avoid dead air
There is also a trimming function within iTunes that works separately from the crossfade solution proposed by @timothymh. This would work better for your dance scenario. If you right-click a song and select Get Info, you get an info window about the song. Under the Options tab, you can set a start and stop point for each song.

As an example, here I've set this song to start 20 seconds from the beginning.