An anagram solver for three words can be found on wordsmith.org. The application there, called Internet Anagram Solver, allows uses to put in any combination or amount of letters and generate all possible anagrams for each combination.
The anagram solver at wordsmith.org also allows users to define certain, special circumstances to further tailor their search results. For example, users can specify that specific letters must appear in all answers or that a certain word must be an exact length. Thewordfinder.com has a similar application, streamlined down to a more basic search of anagrams, though more advanced options, such as the ability to specify the appearance of certain letters, can be added manually.