The ISSA used to publish the printed Slalom! magazine entirely devoted to slalom racing.

www.SlalomSkateboarder.com continues this tradition with an excellent threaded forum which you can use to discuss various topics with fellow slalomers in the world.
There are also articles from the present and the past as well as older issues of Slalom! magazine. 

www.ncdsa.com is also a useful forum for any longboard or slalom related topic.

www.riderz.net is a French forum for longboard and slalom racing.

If you're interested in the sport of skateboard slalom racing make yourself heard and let us know that you're out there.