Lists of more specialized sources for general science, for medicine and other disciplines are available in Library Research Guide for Specialized Resources in the History of Science.
The Historic Scientific Instruments Collection in the Science Center includes over 15,000 instruments, often with contemporary documentation, from 1450 through the 20th century worldwide. The collection also includes other objects from the history of science at Harvard, including William Dandridge Peck's dried fish specimens. Waywiser, online database of the Collection of Historical Scientific Instruments.
Anderson, R. G. W., B. Gee & J. Burnett. 1990. Handlist of Scientific Instrument-makers' Trade Catalogues 1600-1914. Edinburgh: National Museums of Scotland Information Series no 8, 112 pp.
Bedini, S. 1964. Early American Scientific Instruments and Their Makers. Washington, DC: Smithsonian Institution (U. S. National Museum Bulletin no. 231), 196 pp.
--Biographical sketches of 16 instrument makers and an appendix: Mathematical Practitioners and Instrument Makers (pp. 155-171) giving brief data (dates, residence, and specialty) for many more.
Bud, R. & D. Warner, eds. 1998. Instruments of Science: An Historical Encyclopedia. Science Museum, London, and National Museum of American History, Smithsonian Institution in association with Garland Publishing (NY), 709 pp.
Clifton, G. C. 1995. Directory of British Scientific Instrument Makers 1550-1851. Zwemmer in association with the National Maritime Museum, 331 pp.
Epact: Scientific Instruments of Medieval and Renaissance Europe is a digital catalog of over 500 pre-1600 scientific and technical instruments in four Italian, Dutch, and British museums. Catalog entries include pictures.
Holbrook, M., R. G. W. Anderson & D. J. Bryden. 1992. Science Preserved: A Directory of Scientific Instruments in Collections in the United Kingdom and Eire. London: HMSO Books, 271 pp.
Mills, J. M. 1983. Encyclopedia of Antique Scientific Instruments. NY: Facts on File, 255 pp. [Includes biographical sketches]
Morton, A. Q. & J. A. Wess. 1993. Public & Private Science: The King George III Collection. Oxford University Press/London: Science Museum, 710 pp.
Ward, F. A. B. 1981. A Catalogue of European Scientific Instruments in the Department of Medieval and Later Antiquities of the British Museum. London: British Museum Publications, 152 pp., 61 pp. of plates.
Warner, D. J. 1992. Some collections of scientific instruments in the United States. Rittenhouse, v. 7, pp. 97-105.
Many museums have posted searchable collections of online images from their collections.
The Gray Herbarium, Museum of Comparative Zoology, Geological Museum, Peabody Museum of Archaeology and Ethnology, and other Harvard collections offer enormous resources of specimens and accompanying documentaion.