Niwot Ridge Resources
A Source of Information for Mission Critical Systems, Management Processes, and Strategies
Used and New Book Sources
AddAll is a consolidator of used and new book sources and prices
ABEBooks provides search services and rare books.
Alibrus is a book search engine
Book Shelved is an online discussion group for books and book topics
Glasser Rare Books is a very fine store for science and math books.
Jonathan A. Hill is a seller of fine science books.
ISBN.NU is a search and comparison engine
Malaspina Great Books, is hosted by Malaspina College. This is a great source of books and references about books.