Just wanted to add to this to shamelessly bump it, as some have come in here asking questions from time to time about emulators, and this would seriously help them out.
I also wanted to remind those of you who are big fans of emulation, like I am, to check out EmuCR on a somewhat regular basis -
http://www.emucr.com/
Nichole, the person who runs it, updates it constantly. There's new stuff everyday,with recent updates being the latest builds of Altirra (2.0+ test builds), Supermodel (Sega Model 3 arcade), as well as fun stuff like SToid. (An ST emu for android phones)
http://www.emucr.com...20-test-41.html
http://www.emucr.com...model-v02a.html
http://www.emucr.com.../stoid-v10.html
They also have new builds almost every day of Dolphin (now referred to as "Dolphin Git") and PCSX2, which are the best Gamecube/Wii and PS2 emulators.
In the future I do plan on trying to update the main list at the start of this thread, as well as adding stuff for OSX users. (I just have to find a good time when my wife does not constantly need her MacBook Pro)