I've never seen any effect of INT or WIS on the spell saving throws or resistance. I've never seen even an idirect effect, i.e., an effect which is not listed in your personal screen but which reveals itself somehow during the game.
Wis. If you look at the character profile for a character with high Wis they will have a MagDefAdj value. If you compare otherwise identical characters with widely differeny Wis you will see they have different save vs spell base values.
@Nighthawk: I had tried to play with the same character WIS:10->18 and there were no difference in any stats. I tried to cast psionics against him and the effective saves were the same.
My character (wis 21, imported from BG1) was compared to minsc, and they had the same saving throws. so the question remains still, is it helping at all to have better wis and/or int for saving throws?