NDLTD has launched Global ETD Search.
Here's an excerpt from the announcement:
Global ETD Search—developed in partnership with the University of Cape Town, South Africa—is a free service that allows researchers to find ETDs based on keyword, date, institution, language and subject. Researchers may submit queries and view results using the familiar style of popular Web search engines. This new search service will allow researchers to locate relevant theses and dissertations far more effectively than current tools.
Global ETD Search is based on a growing collection of approximately 4 million ETDs from more than 200 universities on all continents. Metadata records are automatically collected daily from individual institutions and consortia. These records form the basis of the search service. Once researchers have located the ETDs of interest, they are able to access the original documents from the originating institutions.