Here is one of the craziest remake projects I have seen: the Q-Gears Final Fantasy Engine. Yup, this guy is creating his own Final Fantasy VII engine. This includes reverse-engineering the data-formats (for the models, backgrounds, scripts,...) so that it can run the game as defined on the original discs.
There is a sourceforge project page which seems somewhat unmaintained. But you can also check the developer's journal for more up to date info and screenshots. Finally, if you really want to get into this you can also check the Qhimm.com forums.