Although this category is technically called defense-special teams in nearly all fantasy leagues, you won't find much mention of that second part in the profiles below. The teams with the very best return games every year still only score about once every three games, if that often. Every other team, of course, is fortunate to produce two return touchdowns in a season. So while Devin Hester certainly adds some value to the Bears, it's generally best to ignore the special-teams component when ranking team defenses. 
The list begins with the unit that I think will easily be the best fantasy defense in 2008 and includes plenty of movement from where you might have gotten used to seeing certain teams. You should generally start thinking about getting a defense after the rounds reach double digits, though I've taken the Vikings as early as the ninth round already. If you don't get one of the top three, you might just as well wait until later and select a team such as Buffalo, whom most fantasy players will probably ignore. 
1. Minnesota Vikings: Anyone who doesn't know about the big change to the Vikings defense just hasn't been paying attention. The draft-week trade for end Jared Allen has the potential to transform Minnesota's entire defense. A pass rush that has stunk for several years gets an obvious boost, where the addition of the reigning sack champ should invigorate Kevin Williams inside and youngster Ray Edwards at left end. That enhanced rush should make like much easier for a secondary that upgraded at safety by signing Madieu Williams away from the Bengals. He and Darre