Glory Dos Days
Aywren beat me to posting this but I had bookmarked the site a couple of days ago: there are 2300+ Classic MS-Dos games waiting for you to play in full emulated in web browser glory. Some defining gaming moments are available, I have been having a lot of fun just browsing the titles available (that style of trip down memory lane may be more enjoyable than actually playing).]
Go look, go play. Nostalgia glory!