Below is a HOWTO written by Nordom for a Gentoo installation of the rt2400 driver. This is until someone creates an ebuild.
as root: 1. cd Module 2. make && make install 3. echo alias ra0 rt2400 > /etc/modules.d/rt2400 4. modules-update 5. cd /etc/init.d 6. ln -s net.eth0 net.ra0 7. Open /etc/conf.d/net with your favourite editor and add line iface_ra0="... your config here ..." - everything is explained by comments in this file 8. /etc/init.d/net.ra0 start 9. rc-update add net.ra0 default