Try these types of searches in Worldcat.Tip for searching for manuscripts: Use "advanced search" and search the "Notes" field for "manuscript+". In many cases it will be necessary to visit sites that have manuscript collections. In some instances copies of specific manuscripts may be requested. Some collections have also been reproduced on microfilm. If this is the case, borrowing or purchasing the film is often possible.
OAIster is a union catalog of digital resources and was developed to test the feasibility of building a portal to open-archive collections using the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH). OAIster can be searched by Title, Author/Creator, Subject, Language or Entire Record. Searches can also be limited by resource type (text, image, audio, video, dataset) and sorted by title, author, date and hit frequency. Results allow further limiting by data contributor (i.e., where the record was harvested from).