Here are some spoilers for the season finale:
Episode 2.23: Live Together, Die Alone (2-hour season finale) (Desmond-centric)
Airdate: May 24, 2006 from 9 to 11 p.m.
05/09 - Damon Lindelof: The finale is "a battle between faith and reason on the same playing field, where it all began." (and some suggest it all began on the plane) Source: Kristin on E!Online
05/08 - Guest starring are Malcolm David Kelley as Walt, Henry Ian Cusick as Desmond, Sam Anderson as Bernard, M.C. Gainey as Mr. Friendly, Michael Emerson as Henry Gale, Clancy Brown as Kelvin Inman, Tania Raymonde as Alex, April Grace as Ms. Klugh, Alan Dale as Charles Widmore, Stephen Page as Master Sergeant, Michael Bowen as Pickett, Sonya Walger as Penelope, Len Cordova as man no. 1, Alex Petrovitch as man no. 2, Eyal Podell as young man and Cathy Foy as receptionist. Source: ABC
General Season 2 spoilers:
05/09 - Libby is not dead, yet. Source: Kristin on E!Online
05/03 - Lindelof ∧ Cuse: We'll see the resolution of the Michael-Walt story. We're going to answer the question of where Michael has been and resolve the story of him and Walt. The growth of Malcolm David Kelly (Walt) will be addressed in the 3rd season. We'll learn more about Dharma. Desmond will shed some more light on his experience on the island in the three years prior to when Locke came down into that hatch. There is more stuff between Sawyer/Kate/Jack, but the focus is not on the romance between those characters. There are bigger fish to fry. Ana-Lucia and Jack were not in a place where we felt it was believable for them to have a romance. Charlie and Claire have been on a break and there's definitely some advancement in their relationship as part of the finale. the perception might be that we dropped the idea of forming an army, what actually happened was that more significant things replaced the need to develop an army. But that concept is indeed coming back for the finale. You can expect to see more of Rousseau next year, but the story of the wrecked research vessel
it will be coming at some point but we can't guarantee it'll be in Season 3. We'll be introducing new characters in Season 3, so you'll be getting fresh flashbacks. You'll probably see fewer flashbacks of our original characters as we begin to move toward certain inevitabilities. You will learn more about some of the other survivors next year. Also, where the new characters come from in Season 3 is going be part of the fun and anticipation over the summer, and hopefully by the end of the finale you'll be getting some sense of who those characters might be. We are going to produce the next 22 hours of Lost in Season 3. Source: Ask Ausiello @ TV Guide