Many people place interesting and/or amusing quotations on their web
pages, as part of thier email signature files, etc.  One particular
source that is referred to numerous times (including the Linux
"fortune" utility) is:

Jack Handley, the New Mexican, 1988

Is this an actual book/movie/whatever, or just something made up by
somebody?

Dear tom_cortese,

Jack Handley is an actual person, and "The New Mexican" is a newspaper
from Santa Fé, New Mexico. In the late 80s, that newspaper published
articles by Jack Handley - obviously one of their journalists -, from
which the quotes derive.
Unfortunately, I have not been able to find out additional detail,
since the public online archives of the "New Mexican" is currently
offline. But in case you need more information on this, you might want
to contact the "New Mexican" editors or librarians, from whom you will
without any doubt get additional help:

The Santa Fé New Mexican
202 E. Marcy Street
Santa Fe, NM 87501

Phone (switchboard): (505) 983-3303
Phone (archives): (505) 986-3057
Fax (archives): (505) 986-3147
E-Mail (general): info@sfnewmexican.com
E-Mail (archives): library@sfnewmexican.com
Website: http://www.santafenewmexican.com/

Sources:

"more slush", by Gene Spafford. Posting in Yucks Digests, 28 Nov 1990
http://www.cerias.purdue.edu/homes/spaf/Yucks/V0/msg00150.html

Library of Congress: Online Catalogue
http://catalog.loc.gov/webvoy.htm

Search terms used:
"the new mexican" "jack handley"
://www.google.de/search?hl=de&ie=UTF-8&oe=UTF-8&newwindow=1&q=%22the+new+mexican%22+%22jack+handley%22&meta=
"Jack Handley" "santa fe"
://www.google.de/search?hl=de&ie=UTF-8&oe=UTF-8&newwindow=1&q=%22Jack+Handley%22+%22santa+fe%22&meta=
handley "I'D LIKE TO BE BURIED INDIAN-STYLE"
://www.google.de/search?hl=de&ie=UTF-8&oe=UTF-8&newwindow=1&q=handley+%22I%27D+LIKE+TO+BE+BURIED+INDIAN-STYLE%22&meta=

Hope this proves helpful!
Best regards,
Scriptor