[mikey]

Starting a blog to spread the word about your company and services is not something new. It is helpful, when done properly. Instead of using a new domain, it would be better to setup a blog on new directory and then link it with the homepage.

As for seo benefits, personally what I have observed is that sub-directories work better than sub-domains if you don't want to build a particular from scratch. SEs consider subdomains as new domains so you'd have to start all over.