Bethesda found a nice little way of squeezing an extra penny from the Elder Scrolls IV: Oblivion crazed fans' pouches. It's not an add-on (at least not yet), just some new objects to make the game a bit more interesting, that are being put up for sale on the OblivionDownloads.com website. The only thing available for now is a Horse Armor Pack (which recently made its way onto the Xbox 360 Marketplace as well), a 6 MB package costing $2 which, obviously enough, gives you some shiny armors to place on any horse you [legitimately] own.
Listed as "Coming Soon", another couple of things will also be available for purchase: the Wizard's Tower of Frostcrag Spire, and the quest to repair the Imperial Orrery of the Mages Guild Inner Sanctum. I just wonder - purely rhetorically - how many hours will it be until those horse armors are leaked down the Internet's torrential drain...
~ 0 hours later ~
...that was quick!
(N.B. Archive text, links removed)