Now in beta a new improved search service for tracing historic websites.
The Open UK Web Archive and the Legal Deposit Web Archive can now be reached from the same search box and it is much easier to browse special collections. You can search for URL (particularly good for tracking down web archived versions of links) and sites which have now disappeared, in particular those from government websites.
On the left of a results page there are a number of facets which allow users to more quickly narrow down results.
Get some more background on the beta system from the British Library blog.