Gamescom 2011 convention in Cologne, Germany are now on sale, so if you're planning to be in the area then (or have the money and time to flit over to the continent whenever you want -- lucky duck), you can see the sights for just a few Euros. The cheapest day passes, at just €6 ($9), are for students and senior citizens, while standard passes are around €10-15 ($14-21).
Note that these tickets are for the public -- they'll let you in the "entertainment area" of the show, but the business side of the event is only for trade and media attendees. But that's no problem. You can still go over there and have yourself a big ol' partyzeit anyway. The convention kicks off on August 17, 2011.