I just read Darth Bane: Dynasty of Evil and it said that Darth Zannah had a mastery of Sith magic. I looked all over the Internet, but couldn't find a description of Sith magic. What kinds of spells can Sith sorcerers perform besides the pitiful showings described on Wookieepedia?
While the main Wookiepedia Sith Magic article does indeed lack a full list,
A great list of Sith Magic is on Wookiepedia category list: http://starwars.wikia.com/wiki/Category:Sith_magic
This article (sourced from Wookiepedia to an extent): http://starwars-exodus.wikia.com/wiki/Sith_Magic: - is fairly comprehensive with a large list of spells. The ones that are more common are:
Aura of uneasiness Memory rub Summon darkness Summon fear Illusion (Sith magic) Force blast Spell of concealment
Darth Aneddu was also a notable practitioner, and like many other practitioners, he was skilled in the preserving of his spirit after death, a skill different than the Force Ghost personified by Jedi such as Obi-wan, Yoda, and Anakin. Many of the notable Sith sorcerors used the ritual of essence transfer.
Andeddu furthered Muur's studies in dark side healing in an attempt to circumvent death, and developed a technique which allowed his mind to live past his physical demise. Through this skill, Andeddu was able to exert control over his dead body, though his mind remained separated from it. His most coveted ability was that of essence transfer, which potentially was a means of immortality. He preserved the secrets of his abilities within a holocron of his own creation; when the device came into contact with his corpse, the life energy of the individual who placed it there was then sapped, and the Dark Lord was resurrected.
According to Darth Wyyrlok, Andeddu's true power lay not in his corporeal form, but within his mind. (source)
"I can use my powers to conjure up your worst nightmares and bring them to life before your eyes. I can drive you mad with fear, shred your sanity, and leave you a raving lunatic for the rest of your life." ―Zannah, describing the effects of her sorcery
She studied the doctrines of the ancient Sith magician Freedon Nadd and mastered his teachings for a variety of effects—covering herself and others in a false light side aura, driving people insane by showing them their greatest fears, or even simply masking her presence in the Force were all within the scope of her abilities...
Zannah's spell of concealment was so strong that its effects lingered on for years after its use. The decade-old remnants of her concealment charm were so powerful that it violently disrupted the psychometry of Darth Cognus when she attempted to read Caleb's hut...
Among her holdout talents was the conjuring of dark side tendrils—negative Force manifestations that appeared in the form of black mist and were capable of disintegrating flesh and bone on contact.
The page on Sith magic has a rather long list of notable practitioners over in the sidebar (note that it scrolls). By looking in the "Powers and abilities" section of each person, you can find more information on different uses of Sith magic (also known as Sith sorcery).