According to the Sun, The Ordinary Boys and The Bravery have both been confirmed. My guess is they’ll both be on Stage 2; The Bravery are playing Oxygen in Ireland on the Saturday, which means they’ll play T on the Sunday. (source)
The Frames are apparently playing too. They’re playing Oxygen on the Saturday, so again, T on the Sunday.. probably in the X Tent?
Bright Eyes is reported to be playing as well - headlining the X Tent maybe?