1st wave of minor leaguers are arriving. The vast majority of these are not worth rostering, but, given your league format (Al- or NL-Only, mixed, keeper/non-keeper), some are noteworthy. Of those notables, most will realize the highest values in single league, keeper formats. For most mixed leagues, keeper and non-keeper, roster expansion means very little.
Mixed:
2B Matt Antonelli San Diego Padres:
Have you seen the middle infield lately? If he recovers his 2007 hitting form, he could be a solid mixed-league middle infielder (double digit HRs and SBs).
LHP Wade LeBlanc San Diego Padres: His AAA ERA was atrocious but his peripherals were not. Pitching in Petco automatically makes him a pitcher to watch.
LHP Jon Niese New York Mets
1B Kila Ki'aihue Kansas City Royals
3B Dallas MacPherson Florida Marlins
OF Jerry Owens Chicago White Sox
OF Ryan Spilborghs Colorado Rockies
OF Adam Jones Baltimore Orioles
LHP Andrew Miller Florida Marlins
AL-Only:
1B Kila Ki'aihue Kansas City Royals: A bad team in need of 1B power. Ki'ahue hit 37 HRs between AA & AAA and walked more than he struck out.
C Taylor Teagarden Texas Rangers
OF Fernando Perez Tampa Bay Rays: The Rays recalled him on 8/31 according to mlb.com. If so, then he can be part of the Rays' play-off roster. 43 SBs in AAA make him someone to watch.
NL-Only:
2B Matt Antonelli San Diego Padres
LHP Wade LeBlanc San Diego Padres
LHP Jon Niese New York Mets
LHP Andrew Miller Florida Marlins
3B Dallas MacPherson Florida Marlins
C J.R. Towles Houston Astros
RHP James MacDonald Los Angeles Dodgers
SS Chin-Lung Hu Los Angeles Dodgers
3B Mat Gamel Milwaukee Brewers
C Angel Salome Milwaukee Brewers
OF Greg Golson Philadelphia Phillies
C Luke Marson Philadelphia Phillies: Catcher is weak across baseball. The fact Marson (and Golson) were recalled by 8/31 makes him a player to watch. The Phillies' disappointment with 2nd-year catcher Carlos Ruiz' bat seems obvious.