This site exists to act as a central repository for free UK postcode databases. Broadly speaking, free in this case means suitable for reuse without restriction.
Since this site was set up, the Ordnance Survey have released the full postcode database under an open licence. You can find the raw data for download under then name "Code-Point Open" on our site (codepo_gb.zip) as well as at the Ordnance Survey's Open Data site.
A geocoder has been put up by a third party at http://www.uk-postcodes.com/. The previous projects that catalysed this side are collecting postcode data from the public and putting it into the public domain:
Register for interest at http://urchin.earth.li/mailman/listinfo/freepostcodes-announce or get involved at http://urchin.earth.li/mailman/listinfo/freepostcodes however it is likely that not much more will happen on these projects.