This week Scirus, the search vertical/metasearch tool that focuses on science information from both the open web and specialized sources, launched the Scirus Repository Search Service. It provides direct access to searchable repositories of material (often full text) from universities and other organizations. You can select repositories and many other databases via the Scirus advanced search page.
On Tuesday, access to T-Space repository from the University of Toronto with over 3,000 documents was made directly accessible via Scirus. The full text of all documents is searchable.
Today, I noticed that the Caltech Collection of Open Digital Archives from the California Institute of Technology is also now directly accessible via Scirus. The archives contains theses, technical reports, preprints, self-archived journal, and other material.
Another excellent metasearch tool that allows you to simultaneously search institutional repositories and other databases containing freely available "academically-oriented digital resources" is OAIster from the University of Michigan. As of today, you can search more than 5,482,333 records from 487 institutions via OAIster.