Standard hypofractioned dose for radical radiotherapy is now 20 x 3Gy.
I don't think anyone suggests it generates fewer side effects, but rather that it doesn't generate more, while being significantly cheaper, and more convenient for the patient. (And we probably don't have enough theraputic radiographers not to be doing hypofractionated treatments.)
SABR/SBRT/Cyberknife takes the hypofractionation (reduction in number of fractions) further, typically down to 5 x 7.5Gy.
There's been talk of two fraction treatments. When we used to do HDR brachy as a monotherapy, that was 2 x 15Gy, but I don't know what the dose is for two external beam fractions.
As Lyn mentioned, the doses for salvage treatments are sometimes different, but I don't know what they typically are.