The ABA is a great source for links to freely-available ethics opinions.
Westlaw subscribers can search individual state ethics opinions by typing the appropriate source name in the search box, and selecting the resulting source from the "Looking for this?" menue. Follow this format: "NAME-OF-STATE Legal Ethics Opinions." For example, for New Jersey, type "New Jersey Legal Ethics Opinions."
Also, the Zief Library has a handful of older state legal ethics opinions in print, as noted below.