Between 1900 and 1986, 30 HR/30 SB seasons were rare:
30 HR/30 SB (1900-1986)
1922 Ken Williams
1956, 1957 Willie Mays
1963 Hank Aaron
1969, 1973, 1975, 1978, 1977 Bobby Bonds
1970 Tommy Harper
1983 Dale Murphy
Starting in 1987, when there were 4 players (Joe Carter, Eric Davis, Howard Johnson, Darryl Strawberry), it become much more common. From 1987-2009, 28 players combined to accomplish it 43 different times. The only season that did not have a 30/30 season from 1987-2009 was the strike-shortened 1994 season, and that was exceedingly close (Barry Bonds had 37 HR and 29 SB).
As of today, there are no players with 30/30. There are 2 players that still have a shot: Carlos Gonzalez and Chris Young.
25 HR/25 BB (2010)
Carlos Gonzalez (Rockies): 33 HR, 25 SB
Chris Young (D-Backs): 26 HR, 27 SB
Gonzalez only has 5 SB since August 24th, and he only has 1 game in 2010 with multiple stolen bases, so this is unlikely. Chris Young has struggled in September (.194, 4 HR, 1 SB), but he is close, and that might give him the incentive to try stealing more bases in the final week. It could end up being very close, but it looks like this could be the first non-strike season since 1986 without a 30/30 season.