To enter "Simply check http://www.stdevel.com/AdventCharityGiveaway.html from 1st to 24th of December, for new items which appear each day. Note down the draw code for the item you want to enter the draw for (max. one per item)." You then have to email "The draw code in the Subject header of the email." and add to the body your name and UK postal address including postcode.
Winners are asked to give a optional donation to their chosen charity.
Update: A list of winners which include TIB editors Andrew Poole and myself winning Pocket RISC OS can be found here.
Link: Press Release