Remaining Major Events in 2008

Mexico City (June 21 – July 6) - A new event that will be part of the Grand Slam series; format and participants not announced yet as far as I know.
ETA (6/21): Apparently this tournament is not happening after all. Chess version of vaporware, I guess.

Dortmund 2008 (June 28 - July 6)
1. Vladimir Kramnik (RUS 2788)
2. Shakhriyar Mamedyarov (AZE 2752)
3. Peter Leko (HUN 2741)
4. Vassily Ivanchuk (UKR 2740)
5. Loek Van Wely (NED 2676)
6. Ian Nepomniachtchi (RUS 2634)
7. Arkadij Naiditsch (GER 2623)
8. Jan Gustafsson (GER 2603)

Grand Prix Tournament in Sochi (July 30 – August 15)

Bilbao (September 2-13) - which will feature the winners of Corus (Aronian, Carlsen), Linares (Anand) and Sofia (Ivanchuk). ETA (8/17): Additional participants are Topalov and Radjabov. Format is a double round robin.

Most important of all is the Anand-Kramnik world championship match (October 14 - November 2)

And of course there's the Olympiad (November 12-25).

And finally the Grand Prix tournament in Qatar (December 13-29)
ETA (11/24): Qatar dropped out; this event will be held in Elista; ChessBase reports that some of the players may drop out. As usual, FIDE has fubared the whole thing.