IntroComp is a yearly IF competition which invites participants to send in the first part of a game. Judges vote on how much they would be interested in playing the rest of the submitted game, and authors who finish and release their pieces within a year are eligible for a prize based on where they placed. The games for 2015 are currently available, and judging is open through August 21.
Below, thoughts on the pieces I ranked highest.
Emily Short's Interactive Storytelling 