If you don't fancy shelling out the best part of £6000 for a pair of Pioneer DVJ-X1s and a decent crossfader, here's a cheaper alternative for budding VJs. It's called "Two You Tube Videos And A Motherfucking Crossfader", and it does exactly what it says on the tin.
Just search for a couple of tracks - we recommend Always Blow On The Pie and Chocolate Rain - hit play on both of them and then crossfade between the two to your heart's content. You can then save your mixes using an open source audio editor like Audacity.
Alternatively, you could use a screencasting application to broadcast your skillz over the Web to a doting audience. Try it out. www.twoyoutubevideosandamotherfuckingcrossfader.com.