If you were interested in computing in the 80s, chances are good that you crossed paths with Apple's venerable II series. There's a pretty great nostalgia factor associated with these machines, so coming across an Apple IIc that has undergone a full upgrade to 2004-era hardware. Charles Mangin over at Mental Hygine successfully upgraded the 1MHz 65C02 and 128K of RAM originally in the IIc to a G4 processor running at 1.4GHz with 1GB of RAM, and even built a VGA adapter that outputs a monochrome NTSC signal. Mangin also retrofitted the keyboard to run through USB via an Arduino box and slapped the innards of an optical mouse in the original mouse shell. While a G4 in this day and age is certainly out-of-date, it's a lot more usable than what was in the computer before, and its a fantastic hack to boot.
If you want to see all the gory details of how Mangin got this computer up and running, check out this Flickr set. This isn't his first Apple "upgrade," either — he previously put a G4 Cube in an original Mac Plus. As for the IIc hack, our favorite part has to be the slot-loading DVD drive he put in to replace the floppy... it may have been a tricky hack, but it looks like it was meant to be there all along.