Kernel newbies

To develop skills at the low level Operating System details, a friend advised www.kernelnewbies.org, where one can find things to do at the kernel level, which are not very difficult, but are a good skill development exercise. Links to other websites as well which have some ideas not specifically related to the kernel itself. One such link is http://people.freebsd.org/~phk/TODO/, which has FreeBSD related tasks.