When I was a dj, portability was one of my biggest considerations in buying equipment. That's why the Numark DJ2Go would be something I'd consider buying. Fits in a backpack, and seems to have all the basics you need to play a party or a weekly bar gig. Here are some excerpts from a couple online reviews (click the link to read the whole thing):
'If you're a wannabe DJ who wants the cheapest, most portable, simplest DJ controller set-up on the market, then get this and a splitter cable and prepare to have a lot of fun.'
- digital dj tips
'If you are new to DJing we recommend picking one up, it won't break the bank, will stand up to a bit of punishment and offers all the basics you'll need to get going.'
- HotDJGear.com
On a side note, just because a review says it's good for beginners doesn't mean experienced dj's can't use it either. Once I moved away from vinyl, I always went for the simplest, smallest equipment I could find.
As of the date of this blog post, it looks like this is going for about $40-50 online. Click the link below to learn more: