German sample manufacturer Realsamples offers a free harpsichord sound for download taken from their "Edition Beurmann" series of historical instruments. The free file features the combined 2x8" registers of a historical Kirckman harpsichord built in 1766. It contains a light version ranging over two octaves with three velocity layers.
The fullrange version, offering 6 different register combinations of the instrument with up to eight velocity layers, can be purchased on the realsamples website: http://sampling-cds.com/index.html?
The light version (GigaStudio3® format, 44.1 khz/16 bits) is available until September 30 and can be downloaded here: http://www.musicianslife.de/2008/08/24/cembaloklang-der-realsamples-