Our time-saving sister, Lifehacker, has shown us the ultimate way to waste time. vNES is a website that lets you play over 200 old-school NES games straight from your browser. From Mega Man to Super Mario Bros, the site even has some Japan-only games (check out Kamen no Ninja - Akakage for some side-scrolling Rolling Thunder meets Ninja Gaiden action). The emulator works on both Macs and PCs. All it requires is Java 1.5 or higher.
i work at a helpdesk, and on saturday's and sunday's when i'm here it gets real slow, another place i like to go for some old school gaming is
check it out if you get a chance, it's pretty insane how many old games they have from nes to sega to game gear