The ClamAV Home Page: www.clamav.net
The amavisd-new Home Page: www.ijs.si/software/amavisd
The amavisd-new Install Instructions: www.ijs.si/software/amavisd/INSTALL
CPAN: www.cpan.org
Dag Wieers' Page: dag.wieers.com
Eicar Anti-Virus Test File: www.eicar.org/anti_virus_test_file.htm
Genco Yilmaz's comprehensive tutorial on setting up your SMTP gateway with Postfix, amavisd-new, ClamAV and so on includes detailed list of required Perl modules for amavisd-new and good ClamAV configuration tips: genco.gen.tc/postfix_virtual.php#virusprotection.
Ralf Spenneberg's Postfix/amavisd-new Tutorial—although ClamAV is not covered, the Postfix configuration advice is particularly helpful: www.spenneberg.com/postfix-amavisd-new.pdf.
Scott Vintinner's Anti-Spam Gateway Tutorial—OpenBSD-centric, it also doesn't cover ClamAV, but it does include instructions on running amavisd-new in a chroot jail, which especially is important if you intend to have amavisd accept TCP connections from other hosts: www.flakshack.com/anti-spam.