Since most U.S. libraries don't collect foreign translations of English-language works, the best way to find out if an English author's work has been translated into a foreign language is to go to the national library of the country where the foreign language is spoken via Libweb:
For example, to find out if Alice Walker's works have been translated into French, choose Europe, Westerm Europe, France, National Library of France, Catalog generale, recherche avancees dans les indexes, enter her name as author (personne) and choose French language.
A similar search for English and American authors translated into Russian can be done in the retrospective catalog of the Rossiiskaia natsional'naia biblioteka, 1725-1998
Searching must be done in Cyrillic and in Russian transliteration of English names, so for example, for Harriet Beecher Stowe enter Бичер-Стоу Гарриет. The catalog is a scanned version of the library's original card catalog.