Go over to the Jedi Outcast mapping forum (
http://www.lucasforums.com/forumdisplay.php?s=&daysprune=&forumid=359), all the editing resources/tutorials there should work the same in JA. Especially check out the editing resources thread. (
http://www.lucasforums.com/showthread.php?s=&threadid=112261)
A great place to get yourself started is RichDiesal's JK2Radiant Mapsource (
http://richdiesal.jedioutcastmaps.com/tutorials/) (tuts are valid for GtkRadiant as well).
An alternative look at the basics of Radiant mapping, as well as some more advanced stuff, can be found in Bubba's Quake tutorials (
http://planetquake.com/bubba/mapping.html)
).
Shameless plug: I keep a small amount of tutorials on my Outcast editing page (
http://wso.williams.edu/~jshoer/outcast.htm). These are not beginning tuts, they are essentially to pick up where RichDiesal left off. Pay attention to the bot routing one!
Map-review.com (
http://map-review.ravencommunity.net/index.php?page=tutorials) now hosts tutorials. Right now we've just got mine and one on scripting NPC's by Heke7, but I think Kengo's working on bringing his SP mapping/cutscene tutorials (
http://www.geocities.com/kengomaps/tutorials.html) over...