From W3C Wiki
HTTP Content Negotiation and RDF
Best Practice Recipes for Publishing RDF Vocabularies describes general principles that are in accord with the W3C Technical Architecture Group's positions on Web Architecture and the use of HTTP for describing "non-information resources".
The "Best Practice Recipes" document provides several recipes addressing the most common cases for RDF namespace documents and illustrates configuration directives for a subset of content negotiation to support serving both RDF and HTML/XHTML documents in response to an HTTP GET on the namespace URI. (The provided examples all use the apache 2 directives; other configurations are soliticted in VocabPublishingRecipes.)
There is only minimal support for content negotiation provided in the document. Citations of libraries to allow vocabulary publishers to do a more complete job of content negotiation are welcome on this page.