Bloom's Literary Reference Online contains both biographical and literary criticism resources.
Academic Search Complete is a multi-subject database that has a decent collection of literary criticism.
Magill On Literature Plus contains both summaries and critical notes over literary works.
Humanities International contains works from all areas of the arts.
Research Library is another multi-subject database
Begin your search with our MLA International Bibliography Database
To begin the search:
1) Type the author's name the search box for the database you want (Wilbur, Richard)
2) Hit enter
Once you are in the database you can be more specific:
1) Formulate a research question (For example: "How does William Shakespeare use A Midsummer Night's Dream to comment on the nature of illusion?"
2) Pull out the main concepts (For example: "William Shakespeare," "A Midsummer Night's Dream," "Illusion")
3) Enter each different conecpt into it's own search box (if there is only one search box you could list all the concepts with the word AND in between each concept).