I've tried hooking an iPod into a standard DJ mixer in the past, but I now do all my DJing with a combination of iTunes (for browsing/searching with my laptop's internal speakers) and Winamp (playing to the house from an external USB sound card). If you need beat matching and whatnot, then you can buy expensive software with all of that built in. It's much, much easier to DJ from a big laptop screen than a tiny iPod screen.