Divine Spellcasting: Divine magic is particularly rare here. With so few deities around to grant it, it's no wonder. Arcane spellcasters are far more common. Many of the spells commonly attributed to divine spellcasters have been reinvented through arcane magic (see the Bard and Medic) or reproduced through other means (such as psionics and spellshaping). Druids, Rangers, Spirit Shamans, and other divine spellcasters who rely on nature more than deities for their spells account for the majority of divine spellcasters. Of those divine spellcasters who draw on deities and ideals for power (such as Clerics and Paladins), most are kobolds, in service to their slumbering dragons, and dwarven priests of Kah Dannist, who still grants spells directly by virtue of his presence. While divine spellcasters can both enslave the magic or work with the magic, the effects of enslaving are less noticeable than with arcane magic, and it is far easier for a divine spellcaster to switch. The difference between enslaving and working with the magic is fundamental to how arcane spellcasters work their art, but with divine spellcasters it is a much higher level aspect of it that can be changed with a little education and minimal effort.
Spontaneous Arcane Spellcasting: Spontaneous arcane spellcasters are more common than in most settings. It's a more natural and intuitive form of magic for those that practice it than divine magic or prepared arcane spellcasting. Most spontaneous spellcasters work with the magic. Members of the magic races very frequently take to spontaneous arcane magic, although individuals who have an aptitude for it are still free to focus their pursuits elsewhere. Kobolds, as always,
Prepared Arcane Spellcasting: Prepared arcane spellcasters are particularly rare in this setting. Most of them are survivors of the apocalypse, members of the old races who were educated when none even conceived of the difference between working with and enslaving the magic. Those survivors, and what few new spellcasters are educated in their methods, almost invariably enslave the magic. Most new practitioners are educated in elven enclaves who insist on keeping their old traditions alive (usually secretly). Extremely few of the magic races practiced prepared arcane magic, but there are a few. Some do so to develop new magical processes, working with the magic, that is either inspired by or is just superficially similar to the way magic was practiced before the apocalypse. Others, rarer still, are merely callous and evil individuals who have no qualms about harming the very fabric of their and their brethren's very beings by enslaving the magic.
Psionics (XPH): Manifesters are common enough sights, although they are vastly outnumbered by spellcasters among the magic races. Dwarves, however, are far more likely to take to the path of the mind than to spellcasting.
Spellshaping: See spontaneous arcane spellcasting. Spellshaping is merely a branch of arcane magic that universally works with the magic, never enslaving it.
Martial Adepts (ToB): Pure Crusaders and Warblades are seen mostly among the elves and dwarves. The magic races are far more prone to mixing in magic with their fighting, and those that study the blade are thus more likely to be spellshapers, Duskblades, Swordsages, or multiclassed Jade Phoenix Mages.
Incarnum (MoI): Meldshaping is a respected spiritual practice among the magic races.
Shadowcasting (ToM): See spontaneous arcane spellcasting.
Binders (ToM): The rituals used by binders are one of the very few things than can connect the inner planes to the planes beyond. It is, however, an extremely difficult task that only experts can achieve any measurable success at.
Truenaming (ToM): The apocalypse messed everything up. What truenames were known before have been irrevocably altered by the catastrophic event. Even the very principles of how truenames are derived have been altered. As such, truename magic is no longer practiced, at least not as it was before. Any practitioners that may now exist are developing the principles anew. (In short, ToM truenaming was how it was before, so if you're going to use truenaming, find a homebrew version of it that doesn't absolutely suck.)
Invocations and other Spell-like Abilities: These magical abilities are inherent powers of the creatures that have them. Asking if they enslave or work with the magic is a meaningless question.