Nominet has announced it is going to accept applications to register a number of specific "short" domains which, for various reasons, it has withheld until now. The process starts on 1 December 2010 when trade mark holders can apply."Short" domains are two and three letter domains like "pa.co.uk" and "3.co.uk". There's a full list of available domains here.
If you are not a registered trade mark holder, then there is a chance for unregistered rights holders to apply in a second sunrise phase which will take place some time in 2011, before a final landrush phase when the domains become available to everyone. More details are available on the Nominet site.