Here are copies of Nixon’s tapes, directly from his presidential library. 

http://www.nixonlibrary.gov/virtuallibrary/tapeexcerpts/

Also, here’s a link to some YouTube excerpts of the Frost / Nixon interviews:

http://groves-us-history.blogspot.com/2009/05/skip-down-for-blog-14.html

A great Watergate website:

http://watergate.info/

A timeline of the Frost / Nixon interviews and a bit of a transcript from some of the interviews:

http://www.historycommons.org/timeline.jsp?timeline=nixon_and_watergate_tmln&nixon_and_watergate_tmln_media_response=nixon_and_watergate_tmln_frost_nixon_interviews