Forgive me if someone posted something like this already. I did search and read through this thread, but was skimming mostly.
I tried using somethief's app (even though closed source exe's posted by a guy in a gaming forum isn't really a safe idea), and couldn't get it to work on my XP SP2 box at home. So, instead I downloaded a wget port for windows here:
http://users.ugent.be/~bpuype/wget/ and then put together this .bat script (just paste this into a file with the suffix .bat or .cmd and execute it from a command prompt):
@echo off
c:
cd "c:\Program Files\Tremulous\base"
dir *.pk3 | find "File(s)" > c:\tremdl.tmp
wget -r -l1 -Apk3 -nd -nc http://tremmap.omgwtf.nl
wget -r -l1 -Apk3 -nd -nc http://download.tuxfamily.org/tremgroup/maps/
wget -r -l1 -Apk3 -nd -nc http://soliter.org/games/tremulous/base/
echo Prior to download:
type c:\tremdl.tmp
echo After download:
dir *.pk3 | find "File(s)"
del c:\tremdl.tmp
cd \
wget needs to be placed in your path (ie. C:\windows\system or in your tremulous\base directory)
You'll notice I have three repositories there. You can add more or remove some, whatever you like.
I'd like to mention that I think it'd be a good idea to put a way to download a map at URL of the server's choice at the time of client connection (make provisions in the config to allow users to list servers they'd "allow" to download from.)
Enjoy.