Well, sort of. The web page for lodge reservations came up at 8am, but was running so slowly that it took an hour to process a reservation for three lodge rooms on a date in April. I think that part of the problem was that the credit card confirmation would time out because the bank wouldn't accept a transaction at that slow a pace.
http://www.travelyosemite.com/lodging/yosemite-valley-lodge/
The pages for Curry Village and the Ahwahnee weren't working yet the last that I checked....