I wonder how many more sites like these are out there? boingboing_net recently featured two favorite games, recreated online in Javascript.

DHTML Lemmings - all levels from Fun to Mayhem, complete with music & "Oh, no!" explosions (requires 500Mhz or better).

Super Mario Bros. - requires Japanese language pack, very little English I could find. Mario looks suspiciously like Hello Kitty in overalls.

Of the two games I prefer Lemmings, but I liked the original Lemmings better than Mario too.