Nintendo Entertainent Sysetm Emulators
 Nestopia
This is the best NES emulator for Windows or OS X. It includes controller support (including the lightgun), online netplay, and support for the Famicom Disk System.
DOWNLOADS
Click to Download Version 1.4.0 (989k)
(LAST UPDATED: June 11, 2008)
Click to Download Version 1.4.1 (2.2MB)
(LAST UPDATED: September 27, 2008)
LINKS
Official Windows Site - News, Downloads, Forum, Tracker, Links, Release Log
Official Mac Site - Download, Features, Screenshot
SCREENSHOTS

 Nesticle
This isn't the best NES emulator anymore, but it was the main NES emulator for years without any problems, and it is very user friendly. This verison is for DOS and Windows 95+.
DOWNLOADS
Click to Download Version 0.42 (329k)
(LAST UPDATED: September 22, 1997)
LINKS
Official Site - Screenshots, Release Log, Patch Archive, Save Game Archive
SCREENSHOTS

No screenshots are available.