looking for reference manager software

[aureli at conti3.sci.uniroma1.it]

I'm looking for freeware/shareware to manage my reference. It'd be able 
to import references from different sources (i.e.medline).
I'm a Mcintosh user, so does anyone know where I can find something?
Thanks

Tommaso Aureli
Dipartimento di Chimica
Universita' "La Sapienza"
P.le Aldo Moro 5, 
00185 Roma (Italy)
aureli at conti3.sci.uniroma1.it