++ Juerd for a good idea.

I am currently using a host of modules which I have varying success with. But as I do most of my work on Win32 platforms I use mostly modules that make my life easier in that environment.

Win32::Daemon	#Manipulate the Win32 Service]
Win32::Process	#Spawn external process'.
Win32::EventLog	#Needed to send messages to the NT eventlog
Win32::EventLog::Message	#Use this and you don't need a Message DLL
Win32::API
XML::Simple	#For the Managed Domain Cust Mapping
File::Copy	#To Move the XML form the xmlout dir to the relevant callout dir
Win32::TieRegistry	#Read and Update/Create Win32 Registry Keys
DBI
DBD::ODBC
CGI
IO::Socket	#Part of Core
IO::Select	#Part of Core
Email::Valid	#Validate email addresses for good form as well as DNS checks

I could go on but theses are really the basis of most of what I do..;)