I'm approaching 100 hours with my Dark Elf (skin dropped to pitch-black, and hair as white as snow like Drow SHOULD have) and her name's Liriel. 2-points to the first person who can guess where I got the name from. Anyways, it's been a while since I've actually played the game, but here's what I've completed, off-hand:

-Mages Guild: Archmage
-Fighters Guild: Guild Master
-Dark Brotherhood: Listener
-Arena: Grand Champion
-I've closed 2 Oblivion gates
-Athletics: Expert (75+)
-Acrobatics: Master (100)
-Sneak: Master (100)
-a bunch of other skills in the Journeyman/Expert levels...

The Mages Guild is the most time-consuming to get through, simply because of the Recommendations you need to get from each of the guild halls in each town. For my relatively high Athletics skill, I made a ring that allowed me to breathe under-water, swam out to the far south of the map and left it swimming for a few hours. I tried to limit my progress to 5 levels per day because it does take a LONG time to increase your athletics. Sneak was the easiest and quickest to get to 100, and I had it before I left the beginning dungeon. Acrobatics was another easy one at that low-ceiling Inn in Bravil.

Oh, and this is with NO mods, NO cheating, and is the PC version...