ADDAX is a free program for transferring files through the Gnutella network. The software is very easy to use and requires very little in the way of configuration.
The interface itself is typical of most other P2P apps, and includes the ubiquitous file finder, library and transfer details, along with a host of options for optimizing your connection.
Besides these standard P2P features, ADDAX also adds some interesting tools such as the ability to add passwords to limit the amount of uploads and the inclusion of a powerful multimedia player.
The finder contains some nice advanced search options which let you find exactly what you're looking for quickly, helping to compensate for the often slow transfer speeds.