I'm trying to get an idea of how much spellpower that 1% crit equals to. I realized that, of course, it depends on how much spellpower you already have. I was curious if anyone knew of a resource or a spread sheet that I could use? I tried a search, but not luck. Anyway, thanks in advance.

Also, sorry to add this, but is there ANY raid usage for spell penetration?

Check this link http://forums.elitistjerks.com/viewtopic.php?id=8603

It has Mage dps calculator (should show you a difference between crit and spell power) in it and has a spell penetration link.

For raids with Locks doing CoE there is little use. I guess if there were no Locks, then spell pen would be useful.

Theorycraft add-on gives you a ballpark figure.

If you're a fire mage, tack on another 1-2 spell dmg value for each crit.

As a fire mage with around 600 spell damage, I'd value 1 crit as 15 spell damage.

No need for -resist pieces for Naxxramas as a mage. There's a rumor saying all lvl61 mobs have 5 resist to all schools of magic, 62s have 10, and 63s have 15. It is not true. Most of them just have 0. The ones I could think of that would have +resist are undead - they might have +10.

The other mobs in the game with resistance are:
Mobs in MC (Ancient Core Hound, Molten Giant/Destroyer, Magmadar, and others). They have 80+ fire resistance so -resist helps vs them.
Azuregos, the whelps clearing to Broodlord Lashlayer, and the dragonkin at Nefarian have some resistance though, and that's when I use my -resist gear.

Level 61 Necro Stalkers have 0 resistances. All bosses in Naxxramas (not 100% sure about KT, I haven't read up on him much) also have 0 resistance to all schools of magic. Negative resistance does nothing.

Carefully.