Check out 3Dbuzz.com They have free video tutorials on using radiant.
They also have video tutorials on making a Quake3 model with Caligari gamespace. That product runs for about 300 bucks but they have a free learning version that lets you make models up to 650 polys.
Even if you don't use or plan on using Gamespace, it is still really helpful to watch the videos because they take you through the entire process of modelling a character for the Q3 engine.
Here's a link to Paul Steed's book for 3DS Max, the guy who created the original Q3 models:
http://www.wordware.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=wwpub&Product_Code=155622088xI've skimmed through the book at the store in the past and it seems pretty complete. He talks a lot about modelling for the Q3 engine and why things are setup the way they are.
Haven't checked these out personally, but their seems to be lots of info here:
http://www.quake3bits.com/htm/tutorials.htmThey appear to be Blender oriented.