LKM and rootkits

Hey ive been trying to learn how to program Loadable Kernel Modules and i was wondering if you guys had any tips about writing them.Perhaps some good books or articles. Also If you knew were i could get some root kits such as adore or something. They are supposed to hide themselves with in the kernel really well. I would love to get my hands on some root kit source code.It would be awsome to be able to modify sys(calls) to hide important data. Any ideas would be great.
Oh and ive already searched on google.I search before i ask ;)

I'm not quite sure you need to be programing LKM's, to use for rootkits, or why you'd you want to modify sys calls, to hide data.. But what you do is your own thing I suppose, if you wish to find a copy of adore.. why not use the ever so popular kiddie search.. packetstorm.