Contact me for anything but bug reports at DELETE_THIS_TEXTaph@oldskool.org
The best start for Atari ST emulation is The Little Green Desktop.
A good start for Amiga emulation is the official UAE homepage.
Download SainT, a very capable Atari STF emulator for Windows that now includes FAST's keyboard processor emulation.
You can check Tand-Em, my Tandy 1000 emulator.