I'm looking to add more content to my Oblivion install in the form of pure dungeon crawls. Right now, I have a personal "rule" for my mod list - no mods that require additional locations, NPCs, voiceovers, etc. Purely content built into the existing regions and areas of the game.

However, I'm extremely interested in mods that add additional caves, dungeons, forts, and ruins to explore, without any additional quests or content outside of the dungeon itself. Do these exist, and any recommendations for good ones?

Hop on over to TESNexus and browse the catagories. Only about 200 dungeons, both vanilla and new content. Should be able to find something that fits your fancy there.