Rudolf's Atari XL/XE Projects (EPROM programmer, 850 interface clone, etc).
Mathy van Nisselroy's memory upgrade *beta* schematic and documentation.
Atari 8-bit Computers: Frequently Asked Questions
Atari 8-bit Hardware Upgrade, Modification, and Add-on FAQ
Atari 8-Bit Computers: Vendors and Developers List
The Unofficial Atari 8-bit New User, Emulator Help FAQ
The following emulators are for the PC, unless otherwise stated:
Atari Peripheral Emulator (APE)
Atari810 - A Disk Drive Emulator
XFormer 2000 (DOS/OS2/Win16/Win32)
Atari800Win PLus (Win32)
Atari M.U.L.E. Online A package containing Atari800Win Plus and Kaillera for playing M.U.L.E. online!
M.E.S.S. (Multi Emulator Super System) (Multi-Platform)
Other files - games, apps, utilities,