The Washington Post features this write-up on an expanded repository of old PC-DOS games, now playable for free in your browser (while it lasts).
It's pretty poorly organized — there's no alphabetical or chronological listing, you just have to search for the game you want (unless I'm missing something). Titles include The Oregon Trail, Master of Orion, The Lion King, Indiana Jones and the Last Crusade, Boulder Dash, Cannon Fodder, Street Fighter II, Bust-a-Move, Lemmings, and many more. Click here for the entire shebang.
A feature in the Post does not bode particularly well for the future of this service, since so many of these games are clearly still active IP owned by major publishers, so do check it out before the Cease and Desist orders arrive.