http://www.dstarinfo.com - A great DStar resource with instructions on operating, Reflector and repeater listings as well as a list of nets and downloadable import files for your DStar radio's.
http://www.dstarusers.org - Last heard listings, repeater listings, etc.
http://www.jfindu.net/PrefixLookup.aspx - Allows you to search for the last heard location and time of a station by callsign.