-Is there a major graphics overhaul?
-Any mods you believe are very good
Check the list of lists, http://tesivpositive.animolious.com/, http://www.tesnexus.com/ (try advanced search and browsing by categories, sorting as preferred), the various release threads (REL/RELz, etc.) around here for recent or recently updated mods, Google if all else fails...
There are lots of little "graphics overhauls" I like to use. But the closest thing to a
complete graphics overhaul would be Vibrant Textures. Mtg Textures would be second most complete. QTP3 or QTP3R next (this one's higher res than vanilla, unlike the previous two). Then... everything else.
http://devnull.sweetdanger.net/obliviontextureoverhaul.html is rather out of date, but it will give you not only some useful mod names and links anyway, but also (more importantly) some basics as to what kinds of mods do what, wrt graphics for Oblivion.
edit: As for what I believe is good... yikes. Where to begin, and most of all, how to stop (posting mod names), in one lifetime anyway.