As of the July 2010 snapshot, this would seem to be how to get Luci working...
1. Load packages
opkg update
opkg install luci-admin-mini luci-admin-full luci-app-firewall luci-app-initmgr luci-theme-openwrt luci-sgi-uhttpd
2. Make sure the web interface comes up
/etc/init.d/uhttpd restart
3. Add the command for #2 to /etc/rc.local (hint: install nano if you dislike vi)