I've personally been involved with online auctions for a long time and I find them to be the best way to explore and find bargains, particularly if you know what you're doing ( there are also public and private repo car auctions offline, but I wouldn't go there if it were my first time around or you could end up a bit lost, to say the least ).
Online auctions, on the other hand, are a friendlier environement for someone new and it's easier to know what's been going on ( checking the average price a particular car is being sold for, who trusted sellers are, how to contact past buyers, etc; you should definitely do all this, by the way ).
You can still check a car's VIN ( vehicle id number ) with a decoder or, even better, run a full vehicle history report with Autocheck ( some sellers even give you this in their listings, but I suggest you do this and everything you need to check the title and condition of the car yourself ).
Here's a page with tips and selected listings of repossessed cars on sale being sold at ebay right now ( the best marketplace in my opinion for this ) and a link to an article with a little more info on repossessed cars for sale .