Other US Computers
Texas Ti-99 Classic99 - (http://www.harmlesslion.com/cgi-bin/showprog.cgi?search=Classic99) - a very nice emulator, emulates every version of the Ti99 and associated hardware. Most of the keys are properly mapped although you have to remember a handful which are in the wrong places. These might all work if you switch to a US keyboard but I like mine in UK mode.
Apple 2e Applewin (http://applewin.berlios.de/) - I am a bit puzzled over the ownership of this one. The link provides version 188.8.131.52 and is accredited to Oliver Schmidt's 1.10.4 source modified by Tom Charlesworth. I also have a version by Michael O'Brien. The only difference is that the latter was developed for Windows 95/NT so must be run in compatibility mode. Nice keyboard mapping though some UK keys are incorrect.
Atari 400/800 XFormer2000 (http://www.emulators.com/download.htm) - a fairly simple program which emulates the Atari 800 as well as the later 800XL and 130XE. Keyboard mapping is mostly correct and it runs a large selection of Atari games. There is no true Atari 400 emulator but since it differed only in having less memory, a different keyboard and only one ROM slot then none of these make any difference in an emulator so just run the 800 in BASIC mode.