An interesting visual representation of 105 of the most common metadata standards.  The chart breaks the standards into four areas:

• domain (i.e., most common field(s) of use)
• community (libraries, museums, publishing industry, etc.)
• function (e.g. controlled vocabulary vs. markup standard)
• purpose (resource description, preservation metadata, rights, technical, etc.)

The accompanying glossary provides a good, basic description of each standard/acronym.

Riley, Jenn. “Seeing Standards: A Visualization of the Metadata Universe,” May 6, 2013. http://www.dlib.indiana.edu/~jenlrile/metadatamap/