This morning I finished entering the catalog of Isabella Stewart Gardner's library into LibraryThing. She had a fascinating and wide-ranging collection: manuscripts from the fifteenth century, incunabula, some great association copies from various crowned heads of Europe, nice collections of contemporary American first editions (Hawthorne, James Russell Lowell, Emerson, &c.), and, as might be expected, many books on the arts.*
Her LT catalog is browsable here.
*NB: I thought it very fitting that I entered ISG's copy of Poe's Tales of the Grotesque and Arabesque (1840) yesterday, on the author's birthday.