Yes there are a few. Most are just free houses in the game (Fighters Stronghold, Wizards Tower etc.) but there are a couple of full DLC updates such as 'The Shivering Isles' and 'Knights of Nine' which add new quests and/or a new world to explore.
not yet the game hasent even been relesed yet!
only on PC. and only user created content
The GOTY edition is just the regular Obivion, but with DLC. So it may be used on the regular Oblivion.
Get the DLC.
It is as are all the DLC for the game
You get the Shivering Isles expansion but the ONLY DLC it comes with is Nights of Nine.
buy all dlc's for oblivion and then buy fallout 3 and buy all the dlc's for it (just kidding u cant get to level 100 the max lvl is 50 but u should buy the dlc's and fallout its awsome)
I got oblivion from games on demand, and i bought the dlc "shivering isles". so, yes.
Unfortunately Bethesda do not sell Oblivion's PC DLC on their own site any longer. That means sadly there is no way to buy most of the DLC for a non-Steam version. Shivering Isles was released on disc, so that's one thing that can be added. But the other DLC packs currently are only available on Steam's GOTY Deluxe edition.
No, it is paid-for DLC.
there is no oblivion trail
The castle is on a DLC The DLC is the fighters DLC... when you buy the DLC you should get a little pop up saying about a castle under attack by maurauders and will give the deed of the castle to whoever saves them... this then becomes a quest and you can go kill the maurauders and claim the castle as your own...
Oblivion doesn't have any online.
The DLC will be free. Not the game.