Tech
1.. RotaryCraft (It's not as mathy as people think, most of it is doubling or halving, and that's not that hard, is it?)
2.. IndustrialCraft 2 Exp (Although it's dependant on other mods, yet maintains it's own power system.)
3.. Thermal Expansion/Ender IO (Both are pretty much even, I like both for different reasons, and cannot really put one above the other, yes I know this is somewhat cheaty.)
Magic
1.. Botania (This is probibly my Number 1 mod overall too, I don't think I'd play a pack without this now.)
2.. Thaumcraft 4 (aside from Sun Scorned.. boy I HATE Sun Scorned... Not that I get burned too much by it thanks to crimson pendant.)
3.. Blood Magic (I only really like the rituals, not the entire mod, so i can't really put this above Thaumcraft which i tend to like as a whole.)
Other
1.. Logistics Pipes
2.. Tinker's Construct
3.. Forestry (More for the trees than the bees... although bees are nice too)
Honorable Mentions:
- Extra Utils
- JABBA
- Binnie's Mods
I should note that alot of these are very close calls for me, especially between numbers 2 and 3 and especially on the other mods.