There are some of the non-standard modules and bundles I use quite often:

• libwww (LWP, etc...)
• libnet (Net::*)
• MailTools
• MimeTools
• MIME::Lite
• XML::Parser
• IO:*

Actually, I could go on and on I guess :) There are really some good tools out there. Visit search.cpan.org and poke around at what is out there.

Cheers,
KM