Mashable has a list of 10 Awesome Vintage Video Games You Can Play Online. I thought this list was, well, awesome, but judging from the comments, its awesomeness might be age-specific. Most of these games were popular right around my prime video gaming period.
Any list that has the original 2D side-scrolling Super Mario Bros. is great, in my book. But even better is the fact that it has the original Legend of Zelda for NES. I used to love that game when I was a kid. I have a working SNES console with Super Mario, but Zelda is a game that I do not have.
I have a feeling I am about to waste a lot of time today.