Here are some of my favourite, but maybe less well known, London and near London related websites that you may find useful

• 18 Stafford Terrace
  A fine example of well preserved late Victorian townhouse & former home of Punch cartoonist Edward Linley Sambourne, tucked away just off Kensington High Street. Open Wednesdays, Saturdays & Sundays for public guided tours.
• Barts Pathology Museum
  A small museum with over 5,000 medical specimens. It's housed in a beautiful glass roofed Victorian building, located within St Bartholomew’s Hospital. At present the museum is only open to the public for special events.
• Benjamin Franklin House
  The House which is the world's only remaining home of Benjamin Franklin, offers Architectural tours on Mondays and Historical Experience tours Wednesdays to Sundays.
• Bletchley Park
  Historic site of secret British codebreaking activities during WWII and birthplace of the modern computer, highly recommend for a fascinating day out within easy reach of London, located only 100 yards away from Bletchley Railway Station in Buckinghamshire.
• British Library
  The UK's national library, love to do my research there but they also have interesting talks and exhibitions.
• Brunel Museum
  A small museum housed in a former Engine House tells the fascinating story of the world's first underground tunnel. Worth looking out for are its regular special events.
• Centre of the Cell
  An unique science centre with a bright orange Pod, filled with interactive games, dramatically suspended above research laboratories.
• Dr Johnson's House
  A small museum located in Dr Samuel Johnson's former home, where he complied A Dictionary of the English Language, also worth looking out for are their special events.
• Fan Museum
  A small, unique museum located in Greenwich with a charming display of fans, particularly recommend visiting on Tuesdays or Sundays afternoons when one can enjoy afternoon tea served in the museum’s beautiful Orangery.
• Geffrye Museum
  English domestic interior in a series of period rooms from 1600 to the present day, great to visit anytime but their annual Christmas Past exhibition is utterly charming.
• Grant Museum
  A zoology museum housing over 65,000 fascinating exhibits, look out for their regular evening film shows concluding with a drinks reception in the museum.
• Gresham College
  Fantastic selection of free public talks on a wide variety of topics.
• Handel House Museum
  This small museum was Handel's former home where he composed his famous Messiah, holds regular intimate concerts and offers regular talks on Saturday at 3pm.
• Household Cavalry Museum
  Tucked away in Horseguards, this small museum explores the role of the Regiment, my favourite part is seeing the horses in their stables.
• Leighton House Museum
  The former home and studio of the Victorian artist Frederic, Lord Leighton with its stunning Arab Hall with its golden dome, intricate mosaics and walls lined with beautiful Islamic tiles.
• Old Operating Theatre
  One of London's most unusual museums exploring the early history of surgery.
• RAF Museum (Royal Air Force)
  A large museum which displays over 100 aircraft housed within five galleries. Telling the story of aviation from the early pioneer days to present times. With free admission and regular special events there is something for everyone.
• Sherlock Holmes Museum
  A small museum which is great fun to visit and explore the world of Holmes and Watson.
• Sir John Soane's Museum
  A fascinating museum located in Soane's former home, particularly recommend visiting during the special candlelit opening on the 1st Tuesday evening of each month, 6-9pm.
• St Albans Signal Box
  There are regular free open days throughout the year of this delighful restored signal box, dating from 1892, with frequent signalling demonstrations and the opportunity to pull the lever yourself, located adjacent to St Albans train station, with easy access to central London.
• Wellcome Collection
  A destination for the incurably curious with an amazing display of medical artefacts and original artworks, exploring the connections between medicine, life and art. Look out for their regular free events and there's also a great café.
• Whitechapel Bell Foundry
  Offers interesting pre-booked tours of the workshop, lead by very knowledgable guides who explain the process of bell making.