I haven't posted for a couple days, which is probably going to be typical. One place you probably already know about to get frequent updates is RLV News/HobbySpace/Space for All. Here are some recent prize-related posts there:
Briefs: Space Explorers in Seattle; Space tourism raffle - RLV News - The raffle prize is a ride on SpaceShipTwo.
Unreasonable tethered test flights - RLV News on one of the Lunar Lander Challengers
Unreasonable tethered test video - RLV News
Unreasonable tethered test results - RLV News
Briefs: TrueZer0 update; Starchaser grant - RLV News on another Lunar Lander Challenger. It looks like they've flipped the order on the site since the RLV News post to be the typical blog order rather than a traditional book order where the latest is on the bottom.
Masten Space update - RLV News - Masten isn't in the LLC this year, but it's good to keep track of them. This is quite a detailed update.
Black Hole Sun advances - Space for All - A space T-shirt design in a contest reaches the top 5.
Operation Immortality a hit; ESA contest for ISS T-shirt - Space for All
Briefs: Anousheh Ansari newsletter; Mars microphone - Space for All - This post covers the What If? contest. A couple months ago this contest was mentioned in an XPF newsletter, as I posted here: May 28 X PRIZE Foundation Newsletter & What If? Competition. The winners are listed in Ansari's newsletter.