network-info
This library provides simple read-only access to the local computer's networking configuration. It is currently capable of getting a list of all the network interfaces and their respective IPv4, IPv6 and MAC addresses.
Compatibility
network-info has been tested and is known to work on Ubuntu 10.10, Mac OS X 10.6.4, FreeBSD 9.0 and Windows XP. It probably works on other flavours of Linux, OS X, FreeBSD and Windows as well.