Retouch Pro's "Library" is a subject directory, which is a collection of websites
selected by people. The result is a database of
quality sites. Because of the human involvement in building a subject directory, the resulting database is small.
A Search Engine's database (like Google) is a collection of websites
gathered by computer. The result is a large database of good, bad, and ugly sites. A search returns millions of "hits" but the searcher needs to determine if the links are related to his search and/or if the sites are "quality" sites.
One advantage of using a subject directory --- it can save you time because someone, rather than something has selected the sites and the results are really about your subject.
The Web contains a number of subject directories. In fact, Google offers a subject directory (The Open Directory Project) that is subject arranged and claims to be "the largest, most comprehensive human-edited directory on the web".
http://www.google.com/dirhp
Searching
Computers --- Software resulted in thousands of good links.
A few other Subject Directories are:
Librarian Index to the Internet: Websites You Can Trust
http://lii.org/
Digital Librarian: a librarian's choice of the best on the web
http://www.digital-librarian.com/
INFOMINE: Scholarly Internet Resource Collections
http://infomine.ucr.edu/