A bit more than a year ago I started working on Multiboot support for NetBSD. This work was completed by the end of past year and was integrated into the main source tree, allowing any user to boot his NetBSD installation by using GRUB alone, without having to chainload different boot loaders.
I've written an introductory article on Multiboot and how NetBSD was converted to support it. It has just been published at ONLamp. Enjoy reading!