I think for a lot of these events, there's a limit to how far people travel for them, so they're known more locally. So instead of a national listing you'll find a bunch of local listings.

Someone posted the www.bicycle-stuff.com up there. It's a good site (note the pictures and reviews). It mainly covers north Texas. There's another site, http://www.bicycletexas.com/ , that is more state-wide, but doesn't have the reviews and pictures.

Note that most of the events are in spring, summer, or early fall- not much coming up. There's a Turkey Roll ride in Denton, and a Happy New Rear Ride in Blue Ridge. Both are good events, but of more local interest.