The author of the book The Social Media Bible has put up his Ten Commandments of Social Media over at the Fast Company Web site. Here's the very first one:
Commandments 1. Thou Shalt Blog (like crazy)
Blog. Please. That's the first priority. Set up a blog, a personal blog, a business blog. It's easier than you think. Use an existing blogging site such as Blogger.com or GOingOn.com or install your own branded blogging site right on your own server by using WordPress. And, WordPress is free.
It's interactive, it's more or less permanent, and it represents exactly what you want to say. The hardest part is doing it on a regular basis, so people keep coming back. Any business that wants to maintain a continuous relationship with its customers should really look into keeping a blog.