We mentioned RedLightGreen last month , but thought we'd urge you to check it out once more by quoting Roy Tennant's statement in his mention in the October 2004 Current Cites  of a good explanation of the innovations of this RLG catalog - Searching RedLightGreen at Princeton University Library .
"If you haven't yet used the RedLightGreen  system from the Research Libraries Group, then stop reading this screed and go try it out. RLG took their Eureka system, a rather huge library catalog, and actually made it usable by normal human beings. There is, in other words, hope for the rest of us that our library catalogs do not need to be as obtuse and painful to use as they are now." Roy Tennant in October 2004 Current Cites.