From Tim Cook: most Intel server boards come preinstalled with their own Network port and IPMI built in. SuperMicro Sells the Add in Card for most of there boards and NEwIsys comes with a form of IPMI built in, but NEWISYS surpasses any of the other board vendors that I have seen when it comes to remote management they actually have a web bases GUI to handle theres, but you will have to pay an arm and a leg for that capability and I think that it is only Opteron based.
You can find some options by searcing for IPMI on pricewatch.com.
FOSS software related to IPMI: http://freshmeat.net/projects/openipmi/ device driver and library OpenIPMI is an effort to create a full-function IPMI system to allow full access to all IPMI information on a server and to abstract it to a level that will make it easy to use. http://freshmeat.net/projects/freeipmi/ userspace IMPI tools GNU FreeIPMI is a suite of packages for controlling hardware that provides an interface compliant with the Intelligent Platform Management Interface (IPMI) specification. http://freshmeat.net/projects/ipmitool/ A command-line utility to control IPMI-enabled devices. IPMItool is a simple command-line interface to systems that support the Intelligent Platform Management Interface (IPMI) specification. It provides the ability to read the SDR and print sensor values, display the contents of the SEL, print FRU information, read and set LAN configuration parameters, perform remote chassis power control, and act as a serial over LAN client. It can work with IPMI-over-LAN (both version 1.5 and 2.0) interfaces as well as the system interface provided by a kernel driver such as OpenIPMI. http://ipmiutil.sourceforge.net/ The IPMI Management Utilities provide a series of utilities that perform common IPMI server management functions, such as setup for the BMC LAN & PEF features (pefconfig). They are designed for end-users, so that they should not require intimate knowledge of how to build IPMI commands. These utilities can be used separately, or merged with a larger server management subsystem. The source license is BSD and ipmiutil compiles under Linux (Makefile) and Windows (doc/mk.bat). There are also corresponding standard HPI utilities that run with two different HPI implementations, including OpenHPI. These were the basis of the current openhpi/clients.
ASL's page about IPMI, including some screenshots that say a thousand words: http://www.aslab.com/support/ipmi.html