Okay, after a bit of a wait (I believe it was several weeks, in fact) 
there's an alternative to Don Stewart's mkcabal.

JoinCabal is available from here:
<http://brokenhut.no-ip.org/~dougal/darcs/joincabal/> or
<http://brokenhut.no-ip.org/~dougal/cgi-bin/darcsweb.cgi?r=JoinCabal;a=summary>

It follows on from my post yesterday about the default licences in 
cabal, in that it'll create a stub source file with a licence header and 
description relevant to the licence you chose. (Apart from the BSD 
licences, which are not well documented. I'll get round to it.)

If you use the [L]GPL a lot then this'll save you a wee bit of time. In 
future I also hope to download licences where I can, straight into the 
LICENSE file.

Full usage can be found in the README. I hope someone finds it useful.

Cheers, D.
-- 
Dougal Stanton