Inside the site dedicated to Sergei Anatolyevich Starostin can be found several dictionaries, as well as the morphological analyzer posted elsewhere by chaika.
The Tower of Babel
In Zalizniak's dictionary several different kinds of searches can be done such as by matching substring, match begging, like begging, or like substring. If substring is too small, too many words are returned.
This dictionary makes it easy to study the prefixed perfective and imperfective verbs of a particular verb. For example, we can individually search for работать and рабатывать under “WORD” using match substring, and click search. The dictionary returns the prefixed (and unprefixed when they exist) verbs for each one. Clicking on the dictionary entries opens up the morphological analyzer with that word. Unfortunately, definitions not always given.
Several other searches are possible, example enter English word in field ‘In any field’, and select TRANS, click search, and all records of Russian words having to do with that English word will be returned by the dictionary. Again, active links returned. Still exploring Starostin’s site, and so I don’t now what all is available.