  Well, seeing as this topic was my idea, it's only fair I should kick off some discussion....! I've been searching around, looking for snippets of information on the value of libraries - here's some of the stuff I found - I'm sure there's lots out there: Articles Eileen G. Abels, Keith W. Cogdill, and Lisl Zach. The contributions of library and information services to hospitals and academic health sciences centers: a preliminary taxonomy, J Med Libr Assoc , 2002 July; 90 (3): 276–284 T. Scott Plutchak. Determining value, J Med Libr Assoc , 2002 July; 90 (3): 273–275 Carol S. Scherrer and Susan Jacobson. New measures for new roles: defining and measuring the current practices of health sciences librarians, J Med Libr Assoc , 2002 April; 90 (2): 164–172. Patrick O'Connor. Determining the impact of health library services on patient care: a review of the literature, Health Inf & Libs Jnl, 19 (1), March 2002, 1-13.
Web-based bits: the urlLink Medical Library Association have a short page on value but the research quoted is early 1990s/late 1980s the National Network of Libraries of Medicine has an urlLink Outreach Evaluation Resource Center which looks at evaluating outreach programmes to measure success I'd be really interested to hear how librarians are tackling this and to see other useful information you've come across. Over to you.... :-) 
