http://www.nfl.com/stats/categorystats?tabSeq=2&statisticCategory=SACKS&conference=ALL&role=OPP&season=2008&seasonType=REG Sacks for last year by team
Top team in the NFL for sacks this season was the Cowboys, with 59 (3.69 per game). Average sacks for all teams was 32.34, which works out to 2 per team per game. Allowing for some GLB inflation, I wouldn't complain if the average number were up to 4 or 5, but the higher numbers should happen when a good D-line meets a worse (but still similarly talented) o-line. Top O-lines should shut teams out most games.
Best o-line last season was a tie between Denver and Tennessee, who allowed 12 each this season. At least 4 shut out games, probably more.