Believe it or not, the St. Louis Rams lead the NFL in penalties in the 2012 regular season, by a wide margin. Maybe if we look back prior to the season and see that the Rams were the youngest team in the NFL, with the youngest offense and the seventh youngest defense, those penalty numbers begin to make more sense. Don't be too worried about these high numbers, Rams fans, at least not yet. As the Rams grow as a team, the penalties should begin to decline.
The Atlanta Falcons had the fewest penalties in the NFL during the 2012 season, and have experience on both sides of the ball. The fundamentals and execution are in place, and the 13-3 record is proof, along with an NFC championship game appearance.
The scourge of the NFL and the new bad boys, those Detroit Lions and Oakland Raiders had 10 teams record more penalties than they did for the 2012 regular season. The Lions recorded 147 penalties in 2011 and 123 in 2012, an improvement overlooked by fans caught up in the after school soap opera some players became involved in.
The Raiders recorded a rather high 189 penalties in 2011 and probably had the largest improvement in execution and discipline on the field in 2012. I know it's hard to swallow this, but that is a positive sign for Raiders fans moving forward.
The entire list is below. This information was gathered from NFL Game Statistics Information Systems.