I found a weapon with both soul trap and fire and when I disenchated it the enchantment was called fiery soul trap and allowed me to have both effects with one enchantment. Are there any other multiple effect enchantments in the game?

Not many, most of them are related to Magicka regen coupled with the various magic schools.

I haven't found any so far on my "main quest play through" toon - who is at 100 enchanting, level 33 (I think, not sure....) and has so many available enchantments I have trouble finding the one I'm looking for....

I never found any, I hope I do. except I do not use weapons because i am a mage, iare there dual-enchant robes/armor?

http://elderscrolls.wikia.com/wiki/Enchanting_%28Skyrim%29 (for example)
Basically Fortify X school + Magicka Regen.

If you double those under normal circumstances, you still end up with your 20% regen, which is nice.