Raikkonen obviously has the talent and the car to win it, but he seems to be making lots of silly mistakes at the moment, which could cost him in the end.
Personally, I reckon Massa would be an excellent outside bet for the championship. He's won as many races as everyone else, but nobody seems to be noticing him and giving him enough credit for it.
Massa is the most improved driver over the last season or two. When Ferrari first signed him I was laughing my leg off thinking, "Ah, here we go, another tea-boy for Schumacher, just in because he's Todt's mate", however, he has come on leaps and bounds by listening to Schumacher for advice. He's not a great overtaker, however, when he's out on his own he's very tough to stop, as Raikkonen found out at the weekend.
Raikkonen is very talented, although makes is some mistakes, but his biggest problem is luck. He never seems to get any. McLaren couldn't give him the car consistently capable of winning championships, and when they did, it was unreliable, so he jumps over to Ferrari, thinking it to be his dream move, and a similar story happens, which is made worse by the fact McLaren have rediscovered their form! (for this year anyway...)
In my opinion Hamilton is the slight favourite, just ahead of Alonso, although the championship is by far from over. Much like Alonso over the last two seasons, it's a case of getting points up the board and not doing anything silly. Even if Ferrari won every race left, as long as he could keep getting podiums and a handful points each race, he should just get the title.

Ayrton Senna: WDC 1988,
1989, 1990, 1991
McLaren: WCC 1974, 1984, 1985, 1988, 1989, 1990, 1991, 1998,
1999, 2007McLaren: WDC 1974, 1976, 1984, 1985, 1986, 1988, 1989, 1990, 1991, 1998, 1999, 2008