Portless claims best reflashed Linksys WRT54G firmware for open network management to date: As part of ongoing work by several community groups, the Linksys WRT54G has become the base platform to try to tap into because Linksys relied so heavily on open-source software in its creation. It took a little cajoling to remind Linksys of these terms, but then they set up this GPL source download center on their site, which is prominently linked from their Support section.
Now, providing the code and giving people direct access to modify firmware are two entirely different objectives, and while Linksys was obliged to do the former, the latter has been the work of many months by several teams who have reverse engineered a number of key elements. The Portless release, say its engineers, relies on and improves the work of other groups and provides a full NoCatAuth portal. (Their software is under the GPL license.)
NoCatAuth is an open network authentication project that allows free networks to offer some controls over who uses it and how, such as bandwidth shaping and a click-through terms of service page that must be agreed to. Presently, you must have a separate computer running NoCatAuth, which adds to the complexity. The Linksys WRT54G, one of the best-selling Wi-Fi gateways of all time, is about $80 street price, making a community node a cheaper proposition.
The article linked to contains a comprehensive survey of similar projects, including news from Less Networks, which is in a technical pre-release at the moment of their modification of the NoCatAuth software for a less Unix savvy installation by average mortals who have the same desire to spread community networking but lack the technical chops.