I'll leave off the usual suspects since everyone already is giving the love to DBI and Template.

• Test::More - I do more testing work than "new coding" (which Randal gets to do). I'll just lump the entire Test::* namespace in with Test::More.
• HTTP::Request - This has always been one of my favorites.
• Mac::Glue - shout outs to Chris Nandor
• Mini::CPAN and Mini::CPAN::Inject - I can put a private CPAN on a CD. I think I have a Perl Journal article on that (or it's coming up).
• DateTime - why can't it be this easy all of the time?
• Net::NNTPClient - I monitor a lot of mailing lists that show up on the perl.org NNTP server so I know what work I need to do.
• IO::All is showing up in quick and dirty scripts, just because it's fun
• Geo::IP - this module, which really means this database, kicks ass. Turn IP numbers into city names. I think I wrote about this for Perl Journal too.
• Pod::Simple - the entire Pod namespace is helpful since I do a lot of Pod work.