7. Comment #184334 by Szkeptik on May 24, 2008 at 4:49 pm
"Prokaryotes are organisms that often have just one cell."

Often? Could someone give me a single example on multicellular procariotes?

Yes. A biofilm; "...a complex aggregation of microorganisms marked by the excretion of a protective and adhesive matrix. Biofilms are also often characterized by surface attachment, structural heterogeneity, genetic diversity, complex community interactions, and an extracellular matrix of polymeric substances". "Biofilms can contain many different types of microorganism, e.g. bacteria, archaea, protozoa, fungi and algae; each group performing specialized metabolic functions. However, some organisms will form monospecies films under certain conditions". (wikipedia)
Dental plaque is probably the one most people would be familiar with.
Ref: Shapiro, J. A. 1998. “Thinking about bacterial populations as multicellular organisms.” Annu. Rev. Microbiol. 52: 81-104.