Sigma went apeshit with new lens releases today. The 50-500, already bigger than your typical WWII U boat, now has OS. They also have some funky new glass (FLD) that is supposed to be cheaper to make than regular flourite elements (and lighter, too). Other notables - a 8-16 lens, 70-200 f2.8 with FLD elements and OS, 17-50 with FLD elements and OS, 85mm f1.4...
Check out DPreviews main page.