Columbia University Libraries
Access 
Access to most site content is open to any users, while access to the actual material is free to CLU community, with some limitations for others; plenty of material is also freely available online.
Fee Policy 
Most site content is open to any users, while access to some full-text papers and to the actual material in the libraries is only for CUL community
Free Retrieved Material
Lots of material retrievable troughout the site, such as abstracts of more than 9,000 working papers, images, and references
Linking Richness
A great variety of links are available on each page, mostly pointing to internal resources and related info pages