Even though he hasn't been officially nominated as the Republican candidate for the Presidency, John Sidney McCain III has the required delegate count and no longer really needs to campaign for more, so it's likely that, barring an accident or other twist of fate, he'll run against either Barack Obama or Hillary Clinton in the November election.
McCain, by the way, was my preferred choice way back in 2000 when he first tried for the brass ring but lost to George W. Bush. He comes from a traditional Navy family (his grandfather was an admiral during WWII, and his dad was a sub skipper in that war and eventually commanded the Pacific Fleet at the time the current Senator was a Navy pilot and POW during the Vietnam War), has a solid record as a member of both houses of Congress, and seems to be pretty fair-minded about many issues.
My only quibble with McCain 2008 is that he seems to be determined to follow the current Administration's policies in Iraq; I'm torn between realizing that we can't pull out all the troops at once like some liberals say we should, and knowing that we can't stay in Iraq indefinitely, which McCain has been quoted (or misquoted) as supporting.
McCain has bucked the trends of the GOP before on other issues, but I'm still afraid that if he wins, he'll be a continuation of George W.. Bush's failed policies.