Resonant modes and taming the room

I measured my listening room and calculated the room modes, and graphed them today. I was trying to determine if/where the resonant frequencies were too closely grouped. Ultimately I was pleasantly surprised by the fact that I do not show any serious problems.
My question though is, how can I tame the room to eliminate the areas of congestion in the modes I am experiencing? Are there differing approaches based on the frequency of the modes?
My room is L 22'-5" x W 12'-10" x H 6'-5". I was concerned about the low ceiling, but it appears to help in this application rather than hinder.
Any insight you might offer would be appreciated.