The book Unearthed Arcana has a large amount of variant rules for the d20 system. Most of these rules can be found at The Hypertext d20 SRD website. (bottom of middle column) A lot of you will recognize some of these variant rules are from the d20 Modern RPG (action points, defense bonuses, incantations). There is an expansive section on variant magic rules. Three variants of particular note are: the Spell Point variant, similar to the BESM d20 approach; the Armor as Damage Reduction variant, again similar to BESM; and the Bell Curve Rolls variant which uses 3d6 instead of 1d20, intended to reduce the chance of extreme results. The best thing about all these variant rules is that there is a section at the beginning called "Metagame Analysis" which examines the effects this rule will have on your game, usually focusing on game balance. As you all know, I am a big fan of GURPS, which is why it should come as no surprise that I like the Bell Curve Roll variant. As stated in "Metagame Analysis: The Bell Curve," balance shifts to the favor of players who rely less on lucky roll sand more on raw character skill and player ingenuity. This system awards bonuses more and rolls less, with bonuses becoming less useful the more adept a character is in a particular skill/subject, encouraging diversification. If, however, you only follow one of these links, I hope it will be the Spell Point varriant. We do, after all, still need to iron out the mechanics of our spellcasting system and this is a spell point based system which has been developed and playtested by the perfesionals at Wizards.