When a NFL player is drafted, he is assigned a draft value(DV) equal to the round he was picked in.  A player retains the same DV throughout the year, even if he is traded.  If he is cut, his DV becomes 0.  When you pick up free agents, the new player assumes the DV of the player you cut to pick him up. If two teams try to pick up the same player, the owner releasing the lowest (more valuable) DV gets him.  The DV is important for future drafts because this will determine what pick a team must give up to keep him.  At the end of the season, all NFL players have 4 subtracted from their DV.  If the number is negative or zero, the player can not be kept and will re-enter the draft pool.  Another example is needed:

The Cormorants drafted the following players:
Favre - Round 1 (no draft value the following year because 1-4 is -3)
Brees - Round 2 (no draft value because he is a college player)
Lewis - Round 3 (no draft value because he is a college player)
Watters - Round 4 (no draft value because 4-4 = 0)
A. Smith - Round 5 (DV=1; he can be kept for a Round 1 pick next year)
...
Rhett - Round 11 (DV=7; he can be kept for a Round 7 pick next year)

and so on.

Thanks to Eric Nelson of the International Fantasy League for introducing me to this system.
This system keeps the best players in the draft pool year after year, but rewards a team for picking good sleepers.  It also makes the free agent game more intriguing.  An example Eric gave was Jerry Rice two years ago when he was injured for the majority of the season.  The owner who drafted him could hold on to him for the whole season, but having drafted him in 2nd round, he couldn't protect him the following year. However, if he released him, an owner could release one of their bench players and pick up Rice cheaply and own him for years.

Another effect is that the college players that use the CTG rule to move from the college roster to the NFL roster can be kept cheaply for a long time.  In our ongoing example, Brees would be kept for the 22nd pick in the draft the year he comes out (if the Cormorants had two players extended scholarships to, they would not have a 23rd or 24th pick).  The following years he can be kept for the 18th, 14th, 10th, 6th, and finally 2nd.  This is the meat of the Cradle To Grave league.  If you draft good NFL prospects in college, you get to keep them for a good number of years cheaply.  Also notice that the fact Brees was drafted in the 2nd round initially is irrelevant because he was a college player.

At least the scoring's got to be easy, right?