http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=141900 -- OMIM link
http://globin.cse.psu.edu/globin/hbvar/menu.html -- HbVar Database
http://www.hgmd.cf.ac.uk/ac/gene.php?gene=HBB -- HGMD Database
http://globin.cse.psu.edu/html/huisman/thals/ -- Huisman's Syllabi (1997)
Each of these links provides a long list of Thalassemia-related mutations with references. The HGMD database seems to be the most complete, but for full access you must be a subscriber.