You can still download the shareware version of Quake from any idgames mirror, including ftp://ftp.idsoftware.com/ . There's also some of the original Windows and GL ports there, but none of the more recent third party ones. You can still buy the full version at idsoftware.com, and I *believe* one of the many packs it was released in is still occasionally available in stores. You can buy the original Dooms quite easily in stores at the moment, as a nice re-boxed version was released just before Doom 3 came out to promote it. I bought it so I'd finally have a legal version of Final Doom...I now have three copies of Doom2, sigh.