Freeside is an open-source billing and account administration package for Internet Service Providers. Features include: Uses Perl's DBI allowing use of almost any database backend to store data (PostgreSQL or MySQL recommended), Web-based interface, Track customers by reseller/agent, Limit the packages a particular agent or class of agents may sell, Tax rates customizable by state and locale, Works with ICRADIUS or Radiator to authenticate directly from SQL databases, Virtual domain support, and more.