One thing I do is to require the person who makes their save to physically move their character/mini to the edge of the effect area. It is a free move and draws no attacks of opportunity since everyone thereabouts is trying to avoid the spell also. This causes some problems, sometimes. I roll a d8 for the random direction of movement.
The second option I use is to say that virtually every spell from any wizard type has oddities to the area/space/person effected. There are small zones with nothing happening, and a character with sufficient skill or luck can spot one and duck into it. Or, through pure chance the spell rolls over and around them in a display of chaos theory at work. (This last bit is not too different from what Claudio Posas posted above).
When I deal with a targeted effect like the old Flame Arrow "firebolt", I explain it as being a spell that primarily affects the person, not their gear, and therefore the target person must have flipped up their heavy cloak to shield them or simply twisted in just the right way to slightly disrupt the spell caster's mental focus on the casting and "aiming."
If none of the above works for the Player, or I start to get an argument that my evil NPC can't do that, I say, "Well, it is magic after all, and sometimes odd stuff manifests oddly."
