All Main Competition finalists are applicable
The stakes are already high for the Independent Games Festival, and the organizers have upped the ante even further by reaching an agreement with Valve for the 2013 event. All Main Competition finalists, ranging from Excellence in Narrative to the Nuovo Award, will get a distribution agreement for Steam should that be a path they would like to pursue.
At this point, it goes without saying that the sheer size of Steam's audience can do wonders for game makers, so this ought to be good news for most designers who participate. The move is also good for players who would not otherwise be exposed to the types of games that the IGF represents, despite Valve's attempt to open access somewhat with Steam Greenlight.