http://www.familyrelatives.com
I should mention that these only include officers.
Years covered include 1847-1849, 1882, and then various years between 1915 and 1945, plus 1952. There is also a list of retired officers from 1947, and records from the Royal Naval College at Dartmouth from 1930 and 1933.
As far as I can see, there is no facility to search across all the lists at once but you have to go through one at a time, but I hope there is one and I've just not noticed it!