Since it's Quake 1's tenth anniversary this year (starting June 22nd) I thought I'd dig up and release all of Quake's original map sources. For all these years the only possible way to glean any information from Quake's internal format was from BSP deconstruction programs - but those had problems with tons of brushes generated from insane BSP splits.
So finally, here are the originals with the dust blown off of them, shined-up and zipped up. Have fun, mappers!
Download Quake Map Sources and run it in an emulator. To use these maps, load them with QERadiant or a modern Quake map tool.