How many super bowls has Brett Favre been in?

As of Super Bowl XLII, two ... Super Bowls XXXI and XXXII. As of the 2007 season, Brett Favre has played in two Super Bowls, winning SB XXXI against the New England Patriots 35-21 and losing SB XXXII to the Denver Broncos 31-24.
Through Super Bowl XLIII, twice.

1) Super Bowl XXXI as the starting QB of the Green Bay Packers. The Packers defeated the New England Patriots, 35-21.

2) Super Bowl XXXII as the starting QB of the Green Bay Packers. The Packers lost to the Denver Broncos, 31-24.
Two (31 and 32), and he won SB 31.