Set collecting is one of those things that you either love or hate -- either the thought of running around in old gear is curiously nostalgic, or you simply don't care to fill your bank with a lot of useless junk. With the introduction of Cataclysm, a lot of these old dungeon sets appear to be changing or disappearing entirely, making them a hot commodity for set collectors. Since a lot of players these days picked up the game in the BC or Wrath eras, not everyone knows where these pieces come from and how to get them.
The first of these sets is the Dungeon Set One. Obtained through various level 60 instances, these blue armor sets were the top of the top before the days of Molten Core and purples everywhere. Originally, these sets had very boring graphics, until a patch was implemented in which all sets got a shiny new graphics update. In the early days of vanilla, these sets were pretty much all players needed to farm for, and the +8 to all resistances that served as a set bonus for each was handy in places like Molten Core, which was nothing but a fun fire factory in which you wanted to stack as much fire resistance as possible. There are nine sets to collect, and each set is class-specific. All set pieces can be found in Stratholme, Scholomance and Blackrock Spire (both lower and upper).