There are hundreds of user created levels - known variously as "mods", "total conversions" or simply "maps", all over the internet. When it comes to finding them though, many URLs are no longer valid, and it is easier to just google for a file name (perhaps adding "quake" as an extra search term) than to try and find the project's homepage - which is probably just dust in the ether now.
To run new maps, place the bsp file into the "quake/id1/maps" subdirectory, and start Quake with the +map MAPNAME option.
Installing mods is simply a matter of creating a subdirectory DIR and extracting the contents of the mod zipfile/tarball into this directory. It is then loaded by using the -game DIR command line option and, sometimes, +map MAPNAME where MAPNAME is the mod's start map.
For both maps and mods, all files should be in lowercase format.
Mod lists can be found at QuakeTerminus and UnderWorld ( Hall of Fame, Recommended). At the DoomWadStation you'll find a comprehensive archive of Quake levels.
A few of the author's favourites are:
Gorgeous medieval themed mod with two single player episodes, a melee style arena mode and nice documentation. Many thanks to Tronwyn, Fat Controller and their co-authors. Link
Epic. Ambitious. Otherwordly. Nehahra is the definitive Quake mod, supported in Linux by LordHavoc's Darkplaces, and QuDos' port of the NehQuake engine. It has some great models and maps, uses fog effects well, and has an (optional) two hour movie/demo which ties-in well with the original Quake "story-line" but is also in desperate need of an edit.
Nehahra also features improved enemy AI - the grunts strafe behind cover, and scrags in open space can be very hard to pin down. New gamers may wish to disable this feature by typing nomonsters 1 at the game console.
A modern mod which made my jaw drop. It also has ambitious sequels: The Lost Chapters and Quoth. Link
Dark and bloody, with Doom's paranoiac atmosphere - a classic. Zerstörer also has some good death match levels - zerstorer
Neil wrote the definitive Half-Life mod "They Hunger". The quality and fun is in these maps too - alba01, alba02, sofsp1, sofsp2, starshp2, Link
Another game requiring the Darkplaces engine, the Hunted Chronicles is a zombie shooter/survival mod in two parts. The second uses fog and lighting effects to spooky effect, and could almost be mistaken for a Half-Life mod. Link
... is a dungeons and dragons themed mod with great monsters and music. It's a little dated now, and the numerous spells can be overwhelming - bmfull
Oum is one of the few Quake 1 mods with a sci-fi feel. It's a well made five level mod with cut-scenes and many new weapons - oum, Link
Coagula is a six level compendium of maps originating from a contest. The novelty is that all maps are floating in the ether, and it's a great set. Link
SdS is a speed run through Mission Pack 1, Scourge of Armagon. Hilarious and amazing. Link
Cracking game-play and rivers of blood - czg07
FQ is a traditional medieval themed conversion. The game has some beautiful levels, but also plenty of raw edges as it was never quite finished. (The project ended prematurely when the web hosting hit a snag). Not all the player classes work perfectly. Use the "g" key twice to purchase items, the "<",">","/" keys for inventory, and the "w","e","r" keys for the grappling hook - fantasy
Here you can get the long lost Fantasy Quake manual.
Little mods with great game-play! - gibfact vigil, museum
Scourge of Armagon by Ritual Entertainment (formerly known as Hipnotic Interactive).
After playing Armagon, you should also check out the Death's Dominion Level Pack.
Dissolution of Eternity by Rogue Entertainment.
- Both official mission packs are generally acknowledged as better than the original game.
Very original Quake total conversion, with the greatest (make believe) machine gun I've ever unleashed. Worth paying for.
Commercial mod now freely available: Link
Xmen mod! Great models. Shame about the game-play. ...When good mods turn bad.
This mod has now been released free of charge, and can be found here.
One of the first commercial mods. It has well modelled and totally new monsters, but the game-play doesn't cut it anymore.
Another first for Quake was the implementation of it's own game language - Quake C. This enables mods to work seamlessly on any operating system. It is possible to install many of the editors which are used to make Quake maps, but creating full scale mods is real voodoo and beyond my knowledge.
GtkRadiant is the only currently maintained and Linux friendly world editor I know of. Link
The Quake Army Knife (QuArK) is a multi-purpose Quake editing tool which.. may or may not have Linux support %-(. Link
...You may be able to find out from the Func_Msgboard - an ongoing hub for Q1 development and new mapping projects.
Bengt Jardrup's homepage has lots of mod friendly stuff.
QuakeForge include some Quake C tools with their tarball.
The Quake Wiki has some relevant links for the windows platforms.