Try http://www.harrier.org.uk for a really thorough coverage of the Harrier both historically and technically. Contributions are invited by the organiser, Michael Pryce, a frequent visitor to the Brooklands archive. The content is extensive and accurate.
International V/STOL Historical Society is devoted to preserving and documenting V/STOL history. A newsletter, the 'V/stol Historian' is published on www.vstol.org.