Having a business blog should affect your site's search engine rankings very positively.
Your business blog will reside on a page that can be searched by search engine spidering software. But that's just the beginning.
Each individual blog entry exists as a separate page that can also be picked up by the search engines. (You'll see a permalink, sometimes symbolized as a "#", at the end of each blog entry.) And as your blog grows, you'll also have blog archive pages that will also exist separately.
If you blog regularly, having so many pages that can be indexed and appear in the search engine listings can only do good things for your site's search engine rankings.
And to make it even better, having a business blog means that your site's blog pages can be included in blog directories and RSS feed directories as well, giving you even more opportunities to build traffic to your site.
