The MIT Libraries
Access 
Non-MIT members can access large amount of basic info, while some e-journals are retrievable in full-text by guests. In most cases, though, an institutional affiliation or individual subscription is required for full access. Plenty of links provided
Fee Policy 
To access many MIT online library contents users need an institutional affiliation, to pay a subscription, or to purchase that specific material -- while the Opac is freely searchable
Free Retrieved Material
There is free access to a large amount of basic info and metadata. Content overview is available and users can choose the resource format (standard, citation, tag)
Linking Richness
A complex linking structure is provided, pointing to internal archives and also to many external resources