Compilations:

Items are edited together into single volumes.

Dictionaries:

Subject-specific dictionaries exist for a variety of topics.

Directories:

A book containing one or more alphabetical lists of the inhabitants of any locality, with their addresses and occupations; also a similar compilation dealing with the members of a particular profession, trade, or association, for example a Clerical or Medical Dictionary, etc. Infomine is good for subject specific directories.

Encyclopedias

Guides:

• Archives and Manuscripts
• Audiovisual
• Databases
• General
• Patents

Handbooks

Patent and Statistical Databases

1. Patents
2. Statistics
3. Reference

Technical Surveys and Reports

1. Archives
2. Audiovisual
3. Copyright
4. General

Thesauri -- Classified list of terms or keywords

1. Archives
2. Art and Architecture
3. Classical Languages
4. Cultures, Anthropology, and Sociology
5. General
6. Law and Politics
7. Museology
8. Music
9. Science and Mathematics

Union Catalogs

National Union Catalog is an example. Another example is OCLC Worldcat.