Obama up to this point has had about 250 million more to work with than McCain. At this point Obama has received around 600 million to McCains 360 million.
Obamas campaign apparently likes to eat a lot.
http://www.opensecrets.org/pres08/expend.php?cycle=2008&cid=N00009638
While McCain must not have as many mouths to feed.
http://www.opensecrets.org/pres08/expend.php?cycle=2008&cid=N00006424
Lots of interesting stats here!!