Koyie Hill on the cubs should about 200 AB's and can actually hit decently.
Keep Ben Sheets on your radar. I think it's pretty likely that he catches on when he is done rehabbing.
Gary Sheffield could be coming to the NL very very soon.
Mark Teahen, Blake Dewitt, Matt Laporta, Jeff Clement all could make solid second half impacts.
Some other sleeper type picks for those really deep leagues:
Austin Kearns, Dimitri Young, Endy Chavez, Melky Cabrera, John Smoltz, Joe Koshansky (just got traded to the rangers, and if salty or davis falters could find quite a few AB's cause he makes a great Adam Dunn/Richie Sexson type of hitter. K or Bomb and not much in between).
I could go on and on, but for upside marginal players I like to look at SB/AB and HR/AB. Those are the guys who when they get hot and someone gets hurt could get some decent playing time for their clubs.