I've found the following sites to be extremely useful or just plain entertaining, so please help yourself and take a look.

http://www.artforums.co.uk/forums	My favourite artist's forum and a good place to find great art.
http://www.rafmuseum.org.uk/	The official website of the marvellous RAF museums at Hendon and Cosford, in the UK. Both are well worth the trip.
http://www.royalnavalmuseum.org/	The website of the Royal Navy museum in Portsmouth, again another excellent museum.