Hello,
I have added ipsets support to openwrt' netfilter.
The packages, with basic installation instructions, are here:
http://openwrt.homelinux.net/ipset/
I'll be building - and placing on the site - a clean source upstream as soon as I figure the right way to do it 
The main project's site, with a little documentations, is here:
http://ipset.netfilter.org/
It still demands a more heavy testing, comments are welcome: sfl.openwrt@terra.com.br
To the official devel guys:
Since some packages are kernel modules, building a .patch from the original buildroot is the 'right' way to do?
If not, how sould I pack the source? I think ipset would be a fine addition to future openwrt relases.
Regards,
Fabio Longarai <longarai@terra.com.br>