Various copies of nmap:
download.insecure.org	official one, dead after 2008
nmap.org		official one, alive only in 2013-2014
nmap.ucsd.edu		old (until 2009?), lost, empty
sourceforge		unofficial mirror on SourceForge until 2014
dist-old		copy from official nmap.org WWW with dates corrected, updated occasionally
dist			copy from official nmap.org WWW with dates corrected, updated occasionally