The good news is that many commercial systems now support standard Z39.50 servers. The bad news is that they can be expensive. Other collections are mostly redundant. But when it comes to unique special collections, each one is important. My ulterior motive for making this presentation is to encourage those of you who are responsible for unique collections to serve those collections on the Internet.
Freeware tools are available to index unique local data structures.
FreeWAIS-sf for the WAIS standard is IMHO the best developed and best supported. Controlled vocabulary from subject-appropriate Thesauri is as important here as elsewhere. Our ultimate weapon to wipe out un-answered questions Serve what you own, own what you serve Local copyright and public domain materials are easy. Quicktime, MPEG Some disciplines has developed specific file formats applicable to the data they use. These formats are certainly appropriate for use in specialized collections.