The Nationals and Phillies split their doubleheader today, and thus split their series.
This was the best possible result for the Cubs; two teams ahead of them in the wild-card race beat each other twice.
Houston's game with Milwaukee is tied 2-2 at this writing; if the Astros win, they'll be in first place in the wild-card race, 6 games ahead of the Cubs; if Milwaukee wins, the Cubs drop behind the Brewers, but will be only 5.5 games behind the Phillies, who will be the leaders.
The Cubs still have to sweep the Rockies this weekend and hope for help from the Pirates, Mets and Brewers (playing the Phillies, Nationals and Astros, respectively), to get to Monday at .500 and with a better shot.
At least today, the game results went in the Cubs' favor, even on a day off.
UPDATE [2005-8-18 21:55:51 by Al]: The Brewers beat the Astros 5-2, and oddly, though that puts the Cubs temporarily in fourth place, it moves them closer to the wild-card lead, since the Astros are no longer leading.