The Aspen Institute
Access 
Aspen is mostly an open access website providing a good quantity of detailed info and research material. Books are only partially downloadable (although free abstracts and tables of contents are provided) and purchasable by pay-per-service.
Fee Policy 
Navigation is free and most material is completely accessible without charge. Some publications and books are retrievable by purchasing a copy
Free Retrieved Material
Free access to a generous number of items, including full-text reports and sample readings. A specific section is devoted to Aspen publications and books are purchasable by payment
Linking Richness
The website is based on a complex internal linking structure, a link to specific webpages being provided for each Aspen project. Connections to other websites and to the Institute's international partners are also available