As you may know, you can read a number of articles dealing with the social and religious life of associations and guilds in the Roman empire by clicking on my full-text online articles (and scrolling down). But I thought I’d mention a few other articles on associations (collegia, thiasoi, synodoi, etc) that are also freely available online:

Our friendly neighbourhood Philo scholar has the following very interesting paper hosted on the Ioudaios site (which later appeared in revised form in the volume edited by John S. Kloppenborg and Stephen G. Wilson):
Torrey Seland, “Philo and the Clubs and Associations of Alexandria.”

The Hendrickson site has Richard S. Ascough’s general discussion (from an edited book) of “Greco-Roman Philosophic, Religious, and Voluntary Associations.”

Ascough’s book on What are they Saying about the Formation of the Pauline Churches, which also has introductory discussions on associations and on mysteries as a backdrop for Pauline groups, is available for browsing on GooglePrint

Ilias Arnaoutoglou, an expert on Greek law, has an article on whether or not there were strictly enforced laws regarding associations in Asia Minor (answering, as do I in my book [pp.161-176], in the negative):
Ilias N. Arnaoutoglou, “Roman Law and Collegia in Asia Minor,” Revue Internationale des droits de l’antiquité 49 (2002): 27-44.