[Kiril]

I only know of Rangers and Dreadknight learnt abilities.
Rangers can learn skills by attacking certain mobs. For Example Wind Talisman, Level 38, 20% Attack speed, learnt in Dargun's Tomb from Burning Eyes Patrollers, Burning Eyes Scouts and all other burning eyes. They also get dropped spells at the high end, dropped in 45+ dungeons, basicaly better group versions of their buffs.
Dreadknights get Cull I at level 30, killing Infineum Gaurdians in CIS, its 400 - 500 lifetap every 10 seconds, very very handy for a DK.
The crashing after learning has been fixed. The way these work is you have to engage the mob, some of them have to hit you, some you have melee them. You can find more by going to class websites.
Psioncist(sp?) are slightly different they learn new spells, beside the ones they get from trainers, from Gesalts they are pink stones dotted around the game, I know one Psion you gets all jumpy when he sees one, pulls alot of aggro in :P