ZA/ZG
Kara
Stonecore
Vortex Pinnacle
Setthek Halls
Stratholme back entrance
Sarth 3D
From the top of my head.
ZA/ZG
Kara
Stonecore
Vortex Pinnacle
Setthek Halls
Stratholme back entrance
Sarth 3D
From the top of my head.
Drake from Stonecore (soloable, just kill the first trash packs with millhouse then sneak past first boss)
Drake from vortex pinacle (soloable)
Raven lord from heroic Sethekk halls (soloable)
White Hawkstrider from heroic Magister terrace (soloable)
Mammoth from VoA 10/25 (soloable archavon, may need group for the others)
Malygos 10/25 (get a partner and 2man it on 10man)
ashes of alar from TK (soloable, but tricky, best done with group)
other than that is mounts from some achievments & repeatables. (argent tourny, Molten front & Tol Barad)
goodluck, & have fun ^^,
When I was bored I ran Magisters Terrace and eventually probably after like 10-15 runs I got the White Hawkstrider. It's on heroic mode, but it's level 70 so it's easily soloable. I got the Raven Lord on my second try in Sethekk Halls Heroic also. You could probably run normal Vortex Pinnacle and try for the flying mount off Altarius, I'm able to solo it as a shadow priest, so I'm sure a DK can. There's also a ground mount in Stratholme off Rivendare, really low drop chance.
You can get Atlas loot, and in the mounts section theres a bunch of lists from rep/dungeons/world bosses etc.
White Hawkstrider is mathematically easier to get than Raven Lord considering the drop rates. You can also get a cool companion from Magisters Terrace which has a decent drop rate as well.