SwiftX - Windows based development enviroment for ANS Forth. Intepreters BasicX - Chip delivered with a basic intepreter. AVR Studio - Atmel's simulator and emulator software. User Guide . It supports the AVA output format and has a gdb like command interface.
Source is available.
UMPS - Microcontroller simulator. Runs under Windows. MicroAsm Download Page - Windows editor that can drive any command line assembler. Works well with IarASM avrasm and avra. Tan Silliksaar's AVR Editor - Dedicated AVR assembly editor for Windows.