Atmora. Home of the Nedes, who then migrated to Tamriel.
To the North of Tamriel, and yes, the Nords came from there, not the Nedes. Nowadays not inhabitable.
Yokuda. Home of the Redguards. Now mostly sunken.
To the west of Tamriel. Not really a continent - Not larger than a typical Tamrielic provicne according to http://www.imperial-library.info/maps/tamriel_westmap.bmp official map. Sinking most likely caused by sword magic after a civil war - "splitting the atomos". Yes, the losing side had some magical nukes, heh.
Thras. Home of the Sloads. Not much about this one.
Also sunken, but as Sloads are amphibious, that doesnt matter greatly to them.
Akavir. Home of Dragons, Tscaesci, Tang Mo, and Ka Po Tun. The Akaviri once fought against the Empire.
The only proper continent besides Tamriel still out there. Described as continent of the beast people, as neither humans nor elves are there (anymore). The Tsaesci once invaded Tamriel, in the interregnum between first and second Empire, actually. Reman, the founder of the Second Empire, repelled them and subjugated teh invading army, forming the core of the imperial legions out of them. The Tsaesci, even though being immortal snake vampries, coudl apparently interbreed with humans. The descendants of the invasion army (nowadays with few Tsaesci blood, looking all human) still live in Rimmen, a town in northernmost Elsweyr.
And those Ice Demons also once tried to invade Morrowind, but were beaten back by the Tribunal and the Underking.
Pyandonea. Home of the Maomer. Mostly island.
South of Tamriel. Not larger then a typcial Tamrielic Province, according to the Daggerfall mages guild globus. maormer said to be truely chameleonic and to have snake magic.
Aldmeris. Home of the Aldmer, descendants of the elves.
Probably never existed as physical place, rather an idea. The shattering fo Aldmeris was the elves first dividing according to their different philosophies.