If you feel like reading up abit on D&D I recomend the players handbbok, complete arcane, complete book of necromantic spells, complete divine, complete psiconic, dragon magic, psiconics handbook, masters of the wild - a druids grove, secret college of necromancy, spell compendium, sword and sorcery - relics and rituals. (yes it's a long list but belive me you do not want to read through every single D&D handbook out there), just make sure you read and get inspierd, try to not copy to much. razz
Anyway I tend to see a few different magic types.
Witch - Not so much a magic user as someone who has knowledge about herbs and nature and can make brews with various effects.
Mage - I see mage and wizard as the same thing more or less. Spellbooks, complicated incantations, scrolls and spellcomponents that they work with, (wand optional xP)
Druid - Can shapeshift some, in tune with nature and can use nature to his/her advantage with the help of minor spells and enchantments.
Elementalist (or whatever you want to call it..) - Works with the elements (I'll leave you to decide which ones.. I prefer the classic 4). They can't work outside their element and usually aren't as strong as wizards but on the other hand dosn't need spell components and usually not spells or incantations either.
Anyway thats just from the top of my head, pretty generic high fantasy stuff more or less, but yhea I hope it helps.
PS: Just make sure you don't overpower your magic users, make sure you put some limits on them, either physically on the magic user (there is only so much the body can take before the magic user collapses) or on the world and magic system itself. But they need limits, a magic user without limits is basiclly a god (if he/she can do anything) and thats no fun.