Cool Standings looks at the standings as they presently are and also tries to predict the winners of games for the rest of the season by taking runs scored (RS) and runs allowed (RA) into account.
They also use another (dubbed the "dumb method") method, which assumes that each team has a 50% chance of winning their future games.
Neither model is very optimistic about the Marlins post-season chances. The most current "smart" model gives the Fish a 14% chance to make the playoffs (with most of the opportunity coming via the Wild Card). The "dumb" model gives the Fish a 23% chance. That makes sense, as the Marlins current schedule is tough (exclusively against clubs wtih an above .500 record from here on out) - so the remaining games will be more difficult to win.
It's also interesting to note that the Mets at nearly 26% (despite being behind the Marlins in the standings at the moment) are pegged to have a better shot at the Wild Card than the Fish. It comes down to scheduling: the Mets have a somewhat easier schedule than the Marlins in September. Not that the Marlins should complain. They got six games against the Devil Rays earlier in the year when the Mets had to face the Yankees (insert Yankees - Rays joke here). What this does point out is the importance of all of those games earlier in the season that the Fish let slip away.
It may not be accurate, but it's at least interesting. I'll add a permanent link to this site beneath the standings table.