Heathkit related Websites
The SEBHC (Society of Eight-Bit Heath Computerists) is an active maillist on google groups dedicated to Eight-Bit Heathkit Computers. Prior to starting the google group, it was hosted on a private server. Those years (2004 - 2007) have been archived here: Archived SEBHC Maillist. Lots of great information is contained in the archive (both for the old maillist and the current one on google groups).
Les Bird's SEBHC site
Les has quite a bit of software, documentation, and photos on Les Bird's Heathkit site
David has made many high quality document scans available on bitbucket.
Doug Miller Virtual Magnolia Microsystems Z89 computer
Doug has additional info and another emulator written in Java for the Heath H89. Virtual Magnolia Microsystems Z89 computer.
Norberto Collado's Heathkit site
Norberto has create new boards to work with and recreate the old Heathkit computers. Some of the boards are available on his site, along with more Heathkit information Norberto Collado's Heathkit site
George Farris's Heathkit site
George has a variety of tools and information for Linux to work with Heathkit computers on George Farris's Heathkit site
Herb Johnson's Heathkit site
Herb site contains a wide range of Heathkit information - Herb Johnson's Heathkit site