CK-12 Foundation
Ck 12: Biology: Mollusks
[Free Registration/Login may be required to access all resource tools.] Discusses characteristics of mollusks.
University of Massachusetts
University of Mass.: Freshwater Mussel Reproduction
This site, which is provided for by the University of Massachusets, gives a very good example of a typical bivalve reproductive cycle.
MadSci Network
What Is the Life Cycle of the Sea Snail?
Good description of the molluscan life cycle as a way of answering the question in the title.