Home Runs for multiple teams: 30, 40, 50.

Through 2015 at least 30 Home Runs (HR) have been hit 1,247 times. For 31 of them the batter played for two teams in that season but no batter played for more than two teams in a season and hit more than 29 HR. The most for a two team season was 58 by Mark McGwire in 1997 when he was traded by the Oakland Athletics (34) to the St. Louis Cardinals (24). Only one player did it before 1949: in 1930 Goose Goslin hit 37 HR playing for the Washington Senators (7) and then the St. Louis Browns (30). Goslin never hit more than 24 HR in any other season. The most recent was Yoenis Cespedes in 2015, traded from the Detroit Tigers (18) to the New York Mets (17): 35 HR.

19 players have hit at least 30 HR at least ten times, led by Hank Aaron and Alex Rodriguez: 15 each.

Gary Sheffield hit at least 30 HR for five teams: Padres, Marlins (42, team record), Dodgers ( 3 times, including 43 in 2000, which tied Duke Snider for team record; broken in 2001 by Shawn Green the next season: 49), Braves, Yankees twice.

Fred McGriff  hit at least 30 HR for five teams, plus twice hit more than 29 for two of those five teams combined:
Blue Jays 3 times, including leading AL (36 in 1989)
Padres twice, including leading NL (35 in 1992)
Padres (18) and Braves (19) combined: 37 in 1993
Braves once: 34 in 1994
Rays once: 32 in 1999
Rays (19) and Cubs (12) combined: 31 in 2001
Cubs once: 30 in 2002

At least 30 HR for four teams:
Jose Canseco: Athletics 5 (including 42 and 44), Rangers, Blue Jays (46), Rays

Alfonso Soriano: Yankees 2, Rangers, Nationals (46 in 2006, team record), Cubs 2, plus Cubs (17) and Yankees (17) combined in 2013: 34

At least 40 HR have been hit 322 times. Babe Ruth was the first to hit 30, 40 and 50: all in 1920 when he hit 54 in his first Yankee season. Ruth hit 40 or more 11 times.

At least 40 HR for three teams:
Jim Thome: Indians 3 (including 52 in 2002, team record), Phillies 2 (including 47 in 2003, leading NL), White Sox
Alex Rodriguez: Mariners 3, Rangers 3 (52, 57, 47), Yankees 2 (48, 54)

At least 50 HR have been hit 43 times. The only players to have done it for more than one team:
Jimmie Foxx: Athletics and Red Sox
Alex Rodriguez: Rangers 2 and Yankees
Mark McGwire: Athletics and Cardinals 2; added 7/19/16 thanks to the comment below.