Atari 800 circa 1979. Came with only 16K back then. Had to upgrade it to get to 48K as they shipped later on.
Did the old acoustic coupler modem (where you dial the other modem manually on the phone, and put the headset of the phone into the modems two suction cups when you hear the other modem answer)! Fun times. 
Did the CompuServe, BBS, Genie, BBS/FidoNet, Internet thing throughout that time as things progressed.
Went from the Atari 800, 800XL, to the 520 ST, Mega ST, Mega STE, Atari TT 030, and finally the Falcon). Still have an Atari 800, 800XL, Mega STE, TT, and Falcon. TT has a Crazy Dots II VME graphics card in it. Loved that computer. Never really used the Falcon just had a great deal fall into my lap I couldn't pass up.
Wrote various programs for the ST line. Did a program for Genie subscribers called "Genies Assistant". Wrote a Caller ID program, Atari Laser Printer Control Panel Extension, and lots of other stuff for the ST line. Loved the Atari stuff.
Went PC after that and played in the DOS/Windows world until moving on to Linux.
In the DOS/Windows days I wrote an Atari 800 emulator called "Pokey" which I released for free. It offered things a few other emulators at the time didn't.
Now I am happy in a Linux world! Do contract programming for a living which is mainly embedded systems, and sadly some Windows code too. Keep looking for an idea for a Linux project to do (and open source).