Look at me, all respondy to my own responses.
I have two more items that change a character's attributes. I think these were more along the line of what you were asking for, Dinonykos. These are both worn items that add a bonus when worn, and remove teh bonus when taken off.
Since there is already a really straight-forward example of this in the database (Gauntlets of Ogre Power, girdle of Giant Strength), I opted for ones that are a little bit more complicated, but should still be easy enough for designers to change to meet their own needs.
First, an item that raises a character's intelligence and improves their saving throw versus Spells. It works for all classes, but if used by a magic user, it doubles the amounts.Diadem of Clear Thoughts
Second, an item that raises a cahcater's dexterity and pick pocket skills. The lower the character's DEX score, he bigger the bonus, and if the character is not a thief or assassin, it gives them the skill of pick pocketing while worn.
Even better, this is from the Dungeon Master's Guide, so I will add this to the default databases.Gauntlets of Dexterity
If there are any questions about how these work, let me know, as I know the answer.