The Broncos still have a better than average cap level because they are no longer a small market team.  At least, that is what I believe is the case...I am often wrong, so wait till SG, HT, Styg or many of the others here to answer your questions more thoroughly. ;)

If my little team were to get a great player, the Yankees only need to buy him away.

Not so in football.  Each team has to be smart because they are all playing with the same amount of salary money.

Another thing I like is that it keeps individual salaries from getting ridiculous.  Let's say a Manning or a Samual demands a new record contract.  A team has to determine if they are willing to proportionatly drop the rest of the team's salaries to make it happen.

The cap is a prime reason why football is doing so well compared to other sports.

For example, the salary cap and collective bargaining go hand-in-hand.  Collective bargaining is where individual corporations are allowed to pool their resources for specific advantages, in the NFL's case, TV contracts and the like.  This is typically forbidden under anti-trust legislation passed back in President Hoover's day (for better or worse), but collective bargaining gets around those federal legal limitations.

The salary cap links to collective bargaining at the point where the television revenue must be divided up among the teams, which is also a complex issue.

If you have specific questions about the salary cap, you should probably aim them at MattR, who seems to have the most thorough understanding of the cap here at MHR (and he tends to have the numbers at his fingertips, though I don't doubt he makes it look a lot easier than it is :)).

Regarding some of your questions:  the cap is for the entire team, no player is exempt.  It does not, however affect coaching staffs (see Redskins) or front offices.  The cap is the same for every team in the league, and has been growing by a few million every year.  I think it may be at 110mil/year?  On top of that, there is talk that unless the league gets some negotiations with the players hashed out in the near future, the possibility of an uncapped season in 2010, I think, is very real.  There are lots of nuances that teams take advantage of, regarding spreading players salaries out over time, or paying them in the form of bonuses (which may or may not count directly against the cap).

Regarding Samuels, they had the same discussion last year about Nate Clemens, who was signed by the 49ers for a record amount for a CB...My own opinion is that the economics are still relatively laissez-faire in regards to player salaries:  some teams will overpay and get caught up in having to have the best player at a position, but the trend against that is to cultivate your own value when the price gets too high, thus driving the prices back down to reasonable market levels.  Still, every so often you see a player get a deal that signals the begining of a new era in paying that position.  An example of this would be Peyton Manning's contract.

And a trend that you will get used to in the NFL is that every year the Superbowl winners get their free agents picked clean.  There isn't a logical explanation, though there are some psychological theories, but for the last several years now, the NFL World Champion has had a lot of trouble keeping all of their free agents.  I guess the FAs look better with a ring on!

Lastly, in the spirit of full disclosure, you should know that the Broncos under Shanahan got into Patriot-like trouble several years ago with their own "creative" practices of keeping the team "under the cap."  It cost them a third round draft pick, which the league made them forfeit, much like the Patriots are forfeiting their 1st rounder this year.  I'm sure some of the MHR guys and gals who recall it better than I do can give you more details.  The caveat is that the teams were still in the infancy of the cap and figuring out how it worked.  Denver's particular way of 'tweaking' the cap was found to be unacceptable AFTER the fact.

Bonus:  I just keep thinking of things to say here...lastly I wanted to bring up the practice squad.  Every NFL team is allowed to have a practice squad that has several young players on it.  The rules regarding player eligibility revolve around how much time they have actually spent on the NFL field.  It is a recent development which teams are still figuring out how to work to their best advantage.  These players are in addition to the regular 53-man roster which is governed by the salary cap, so I think these players may not count against the cap.  I could be wrong on that point though.

1. The cap is good. Makes people responsible, and the game fair.
2. Giants have all of their key players locked up, excpet for FS Wilson. They other guys are just scrubs and backups.