Right now:
Athletics* 26 games over .500
Brewers* 21 games over .500
Angels 20 games over .500
Dodgers* and Orioles* 16 games over .500
Tigers* 12 games over .500
Nationals* 11 games over .500
Giants 9 games over .500
Pirates 8 games over .500
Yankees and Blue Jays 6 games over .500
------------------------------------------------------------no team at .500
White Sox 6 games under .500
Mets 7 games under .500
Padres 10 games under .500
Twins‡ and Phillies‡ 11 games under .500
Red Sox‡ 14 games under .500
Cubs‡ 16 games under .500
Astros 21 games under .500
Rangers‡ and Rockies‡ 24 games under .500
*Best Record in their league
*Leading their division
‡Worst Record in their league
‡Cellar in their division
Could be worse. The Yankees and Dodgers are getting streaky right now.
EDIT: Corrected as per BeeSO's correct diagnosis.