The NFL has maintained a competitive environment by limiting how much teams can spend on the payroll.  That number has been going up so fast however that only eight teams are within 3 million dollars of it; only 12 within six million.  In baseball the big market teams can be competitive every year, because they can outspend the competition up to 10 to 1 and pick up all the great free agents.  Football has done much better at keeping all the teams competitive with a combination of the cap and allocating draft choices based on record.  The cap was 85 million in 2005, 102 in 2006; 116 million this year; that's almost 50% over four years.  If you look at payroll some teams, like the Titans, 49ers, Dolphins and Bills are in the 80-90 million range.  The teams at the top (Panthers, Colts, Redskins & Rams) are coming out at 112-123 million.  Teams can game that top 116 million with 'bonus' clauses that can't be achieved.  Here are the teams ranked by payroll:

So roughly half the teams are not even within 20 million of the cap, and the teams that spend the most are more than 50% higher than those that spend the least.  The cap has gone so high that it is almost not a cap anymore, income is.  Now the NFL has opted out of the Collective Bargaining Agreement, that means that there will be caps for 09 and 2010, but if nothing happens 2011 will be uncapped and the NFL could be headed to less competition.  I'd hate to see the NFL go the way of baseball where the teams location has more to do with success than any other factor.