Here are my predictions for the series:
Game 1, Monday August 15 at 7:05 PM CT. Rodrigo Lopez (3-3, 4.78 ERA) vs. Henry Sosa (0-1, 6.00 ERA).
Cubs win 6-2, because I've never really heard of Henry Sosa. I say Lopez goes 7 innings, 2 runs.
Game 2, Tuesday August 16 at 7:05 PM CT. Ryan Dempster (10-8, 4.70 ERA) vs. Brett Myers (3-12, 4.71 ERA).
Cubs win 4-3. Dempster and Myers each go 6 innings, and Marmol holds on for the save.
Game 3, Wednesday August 16 at 1:05 CT. Casey Coleman (2-4, 7.23 ERA) vs. To Be Announced (but most likely Bud Norris, 5-8, 3.55 ERA).
I really think Norris will pitch a good game, and Coleman won't, but because the Astros bullpen (and entire team, for that matter) suck so bad, the Cubs will rally late and win 7-5.