Plone and Drupal are two of the best known and most popular content management systems, and both make excellent platforms for community networks.

Feature for feature, both are extensible, template-based systems that can be used "out of the box" or have the ability to be customized extensively. Plone is based on Zope, so it could be characterized as a more mature product. Drupal was built from scratch, and is somewhat younger, but is also robust (Drupal powered Howard Dean's Web site).

How would you pick one over the other?

One key difference is the scripting languages used by each product. Drupal uses PHP, while Plone uses Python, a scripting language derived from Perl. If you plan to do any customization (and you probably will want to do a little), you may want to pick one of the other based on the programming and tech support available. If you have several Python or Perl folks, you probably want to pick Plone. If you have access to PHP expertise, you'll probably want to go with Drupal.