HTML::Template does exactly what I need and does it well. Can't ask for anything better than that. Extremely easy to use, fast, mature, stable. If your templating needs do not extend to one of the heavyweights (Mason, Template Toolkit), then you really can't go wrong with HTML::Template.
Another module that is used heavily here at work. Thorough documentation, nice API, easy to use. We've managed to automate a *lot* of very mundane and time consuming reporting thanks to Spreadsheet::WriteExcel.
A fantastic module with very thorough documentation and a nice API. As a matter of fact we wouldn't be using Perl for a lot of our projects at work if it wasn't for DBI. Best module on the CPAN? Hmm, top 5 for sure.