Interlink Networks - Providers of servers, network appliances and consulting. Site includes user group functionality.

radiusContext - A python log analyzer for servers. Available under the Open Source license. Includes advantages and disadvantages, usage information, and latest features.

WinRadius - Standard RADIUS server for network authentication and accounting.

CERT Advisory: Vulnerabilities in Various Implementations of the RADIUS Protocol - Covers two vulnerabilities: the digest calculation buffer overflow, and the inadequate validation of the vendor-length of vendor-specific attributes. (March 4, 2002)