RangerWickett said:
I'd like a simple magic system that could cover all that. I don't know if simple is possible, though. I'm just brainstorming here, right now.
That's basically the take that Mage puts on it.
The Incantation system from Urban Arcana might work better for you. That has the 'big effect, bad consequences if you screw up'-type mechanic you seem to want.
Another place to look is the 1922 Golden Bough by James Frazier, certainly one of the most exhaustive anthopological classifications of world magic and belief systems ever undertaken. You'll want the latest edition one because the 1890's version is like 12 thick volumes. It's a little dense. You'll know the basics, like sympathetic magic, from the basic D&D stuff but this goes into a lot more detail.
One of the best and most gameable 'real world' magic systems I've ever seen is in
GURPS Voodoo, which uses initiation levels, being ridden by spirits, etc. Their Spirits book also does more with the Ritual Magic idea.
Modern Magic by Green Ronin has d20 Modern magic of several sorts, including some 'real world' practices.
To really model real world practices, use
Mutants and Masterminds; mages get
one superpower: Luck Manipulation, along with a generous GM sense of balance. They just make things that could happen normally more or less likely to happen.
I haven't seen the urban fantasy book from Guardians of Order yet (Teflon Billy has it and has promised a review); usually the urban fantasy genre has a smattering of real world-based practices.