Black Hardware Information: Various topics relating to NeXT.
Black Hole, Inc.: Reseller of NeXT hardware and NeXTSTEP and OpenSTEP software, and Intel-based systems designed for OpenSTEP.
Heller's NeXT pages: A useful collection of information for working with and around NeXT boxes. Includes many FAQs, schematics and some interesting power supply fixes.
NetBSD/next68k: NetBSD port to NeXT hardware and project page. Works on all 68040 non-ADB models.
NeXT Hardware E-Group: NeXT hardware and OS problems and solutions. Low traffic.
The NeXT Information Archive: A repository for information on NeXTSTEP, OpenSTEP and Rhapsody. Many pictures and scans.