Scenario: 7 HD displays connected to two sources (Set-top box, and a Mac comptuer). The TVs already have a single Cat5 cable runnign to each. Ideally supporting 1080p, or at least 720p resolution. A cost effective solution that will not require an expensive distribution matrix.

2X2 HDMI MATRIX SWITCH
$449.10

The best solution I found was availble from Atlona using a HDMI 2 x 2 matrix that will feed two 4 port HDMI splitters Using that solution, you could have all 7 displays show the same thing, but it would also give you the option of splitting the signal so that three TVs recieve one signal, while the other 4 recieve another... without having to go for the full matrix now.

HDMI EXTENDER OVER SINGLE CAT5 UP TO 120FT
$324.95

These are not HDMI distribution amplifiers, nearly all the distribution amplifiers require two cat5 cables to support HDMI. However Atlona has an innovative HDMI extender over a single Cat5 that can extend up to 130 feet (Or up to 200 feet for 1080i/720p) In your situation, you would need 7 extenders.

Atlona 1x4 HDMI Distribution Amplifier
$314.99

There are a few other options. You could exchange the 2 x 2 matrix and the two 4 port splitters for a 2 port switch and a 1x8 splitter. We also have some DVI passive extenders, however they do not support HDCP and only support distances between 50 and 100 feet.