Statement: Given that discipline-specific online databases are frequently used by students and researchers to find relevant articles in the sciences and technology, publishers of conference proceedings should strive to have their content (keywords, abstracts, or full text content) indexed in the most relevant online indexes and databases in their fields.
Furthermore, conference publishers should allow or encourage the harvesting of their metadata and/or crawling of their full text content by Internet search engines such as Google (and Google Scholar), Science.gov, WorldWideScience.org, Scitopia.org, and Scirus.org according to a standard protocol such as the Open Archives Initiative (OAI) Protocol for Metadata Harvesting . Where they do not already exist, relevant metadata extensions should be developed to more accurately represent conference documents. Such extensions can include information such as a standard full conference name (see "Naming Consistency" section) and conference abbreviation.
Finally, it is preferred that the full text of conference papers, rather than just the citations and abstracts, be indexed by the conference publisher or vendor. Good metadata being essential to the findability of documents, publishers should also use a standard metadata format. Any metadata standards used by the publisher should be prominently noted on the online access site.
Rationale: Conference papers that are not indexed in the most relevant indexes and databases in a field are, for all intents and purposes, non-existent as far as other researchers are concerned. In addition, it has become apparent with the development of more and more powerful Internet search engines that scholarly publishers that share their indexes and metadata with search engines will find their material more widely accessible to other researchers in citation/abstract format (if not in full text) due to the obiquity of Internet searching in scholarship. For example, Google Scholar has become a well known and well used scholarly search index. Making scholarly research from conference papers more widely accessible will make researchers more aware of what has been done in their field.
Best Practice Examples: Scholarly associations that share their indexing with Internet search engines include the following from the Scitopia.org site:  American Society of Civil Engineers; American Society of Mechanical Engineers; Audio Engineering Society; IEEE; Society for Industrial & Applied Mathematics; Society of Automotive Engineers; and SPIE. (This is an incomplete list. For the complete list, please see the Scitopia.org site.)
Large professional associations or publishers that appear to share their citation, abstract, or full text indexing with Google Scholar:  American Chemical Society; American Concrete Institute; American Institute of Aeronautics and Astronautics; American Mathematical Society; American Physical Society; Association for Computing Machinery; Electrochemical Society; IEEE; Institute of Physics; Institution of Mechanical Engineers; National Academy of Sciences, and Springer (which publishes conference proceedings as part of its various eBooks.
IEEE is probably the best example of web indexing. Any search done in the regular Google search engine on topics related to electrical and computer engineering will routinely bring up relevant papers in the IEEE Xplore digital library. Frequently abstracts are accessible in this way, even to those who do not have a subscription to the full text. The value of such accessibility to scholarly work in this area is immeasurable.
An example of a smaller professional organization whose publications appear to be indexed by Google Scholar is the Society of Tribologists and Lubrication Engineers. Their conference articles are frequently published by Informaworld.com in the journal Tribology Transactions.
Other smaller professional organizations whose proceedings are published and indexed as part of Springer's Lecture Notes in Computer Science series: Indian Conference on Logic (a.k.a Indian Conference on Logic and Its Applications); International Symposium on Visual Computing (ISVC); International Workshop on Languages and Compilers for Parallel Computing (LCPC). In each case, papers are available online in PDF format. Papers in the Lecture Notes series are browsable by author, date, paper category, paper/chapter title. Papers are NOT browsable by conference name or title. Every paper is given a DOI as well.
comment (Tracy)1/6/09: thinking about smaller conferences - should the best practice examples include conferences that are published in conference series - like Lecture Notes in Computer Science? Or are there any smaller conferences/associations that get their materials indexed in the databases? Should we include those that publish in special issues of journals?
Ed comment 1/7/09: I'm working on this. I've also addressed indexing of conference papers in online databases above, because I somehow left this out in my initial draft.
Ed comment 2/2/09: I believe that I have addressed the issue of smaller conferences above in the "Best Practices" section.