Foyle Special Collections Library and the Tony Arnold Library in the Institute of Taxation. This last collection joined the Kings College London law collection in 2001.
The Foyle Special Collection Library offers over 130,000 items ranging from human anatomy to theology and dating as far back as the fifteenth century. Archives are held at the King's College London Archives at the Strand Campus. Seminars and classes are held in this section, among others, to promote the services of the library and proper handling of materials. This also encourages a connection between librarians and faculty to utilize the collection to the max. There are also thematic seminars that explore specific areas of the collections.
Last year the BBC filmed a short program on an interesting item in the Rare Books Collection by William Henry Ireland; Miscellaneous papers and legal instruments under the hand and seal of William Shakespeare (London, 1796). This would have been an interesting item to witness. Ireland was able to fool a large number of people in that these were rare letters and even extra scenes to Hamlet and King Lear, but was caught when the papers were published since scholars now had the chance to examine them!
There was an interesting exhibit "Explore 500 Years of World History" offering a close look at the collection of the Foreign and Commonwealth Office. According to the Exhibition Guide, this is "one of the most important acquisitions in the long history of the College's library" and is "the most heavily used". What I particularly liked about the items is that they were hand selected not only by the curators, but by visitors such as historians, diplomats, film-makers, and graduates.
Take a virtual tour of the library at http://www.kcl.ac.uk/virtualtour/maughan-library.html