A large number of bar associations provide a benefit to members that gives them access to legal research services as part of annual association dues. For people wanting to compare these benefits across the United States, there's now an online map and matrix of related benefits from bar associations.
Here's a static version of the map, which you can also find here: Don't Know What Free Legal Resources Your State Bar Provides You? Here's a Map!
This map is from the 3 Geeks and a Law Blog site, where they strongly suggest that lawyers should "check out your bar association and see what they have to offer". The site's underlying data comes from a more detailed matrix of bar benefits that describes such benefits as mentor and ethics resources.
Legal research bar benefit services are provided by companies like Fastcase, Casemaker, Loislaw and Versuslaw. These services tend to provide more options than free sources such as Cornell's Legal Information Institute or Google Scholar Legal Opinions and Journals. At the same time, they don't provide the feature set of premium services such as Lexis or Westlaw. One thing to note: coverage may vary from bar-to-bar.
Back in December, two Georgetown law librarians gave a presentation focused on options for integrating low-cost legal research alternatives in private law firms. Part of this program suggested leveraging existing bar benefits. Materials from that event are online here: