Updated: The Twitterites inform that this is a faster download link:
http://parlvid.mysociety.org:81/os/

Well it finally happened some nice big datasets are now available, visit these sites for more details:

http://data.gov.uk/data/publicbody/Ordnance%2520Survey

https://www.ordnancesurvey.co.uk/opendatadownload/products.html

I will hopefully have an opinion on what’s been released later but for the moment just enjoy the idea that you can easily (provided the server is not down) download (shapefiles and the like).   Select the data you want (either as a DVD or download) then give them your email address, they will then send you a link for downloaded your fresh datasets.

I have downloaded the boundaryline dataset and opened it up in ArcGIS, it even has Parish boundaries…. now what do I do with it all?

Keep trying on the site as it obviously has been working very hard this morning to stay afloat!  My suggestion is to wait until the evening (or a couple of days) to do the downloads.