It seems like you’re asking for an actual, fully-fledged online school and not something like Digital-Tutors, which has already been recommended. These do exist, but the tuition is far, far higher than something like CGWorkshops (http://training.cgsociety.org/), which offer short-term 3-8 week courses, complete with one-to-one tutor support.
Those of which come to mind right away are Escape Studios (http://www.escapestudios.com/) and FullSail (http://www.fullsail.edu/online-education). The latter of the two, from my understanding is the more expensive in tuition fees, though it comes with a host of goodies such as providing each student with a Mac.
More realistically for most people, I would suggest taking a look at courses offered by 3DMotive, 3DTotal, Eat3D, InfiniteSkills or one of the other online material providers. There’s some fantastic resources out there, with very low-cost entry fees. It’d probably be advisable to look into those first.