Sims 3 mods

Nrass -
Overwatch
Master controller
Errortrap


These 3 should keep your game running smooth.

I would add NRaas Register, Traffic, to an extent GoHere, and Traveler (if world travel of any kind is to be in play) to that list.

But for a more comprehensive look:
http://nraas.wikispaces.com/Tips%20For%20Better%20Game%20Performance :)

One also has to take the specs of one's system into account when playing with all 11 EPs. Some will be fine, some will need extra help along the way to keep things running smoothly, and some systems are just too under-powered to handle all of that stress no matter what we do with them. Pets and Seasons are the heaviest hitting EPs, followed by IP and ITF.