Blog
A blog is simply a specialist column-like feature on your own website. The latest posting is at the top, with earlier postings below or in an archive. In business, the blog is used to disseminate information in a chatty rather than a formal voice, or as an executive summary or review of longer and more technical information. It's not usually as polished as a web page or article, and can contain a great deal of musing or opinion rather than hard facts, as long as you make it clear. This is where the owner or executive of the company can let their hair down, as long as they keep in mind that this is still a public arena.
While blog entries can be similar to articles, blogs die if they don't have new content and entries on a consistent basis. A blog is a commitment. When your blog is part of your website, it improves your search engine hits as long as you are consistently speaking on topics relevant to the people you want visiting your website.
You can have a blog directly on your website OR you can link to a blog service on another website. A blog on an external website will not increase traffic directly to your website, so if you use an external blog service, make sure to include links back to your website in your posts.
A blog should contain useful information for your potential clients, policy changes, getting to know you or your company, research results, tips & tricks, product reviews, service changes, industry news, relevant ramblings, company news, upcoming event announcements, and just about anything else. Beware alienating the readers, though. If you're not delivering value in terms of useful information or option to the readers, they won't come back.
Again, the most important facet of a blog is consistency. Post regularly -- weekly or daily. If you can come up with a good list of potential topics to post on before committing to a blog, all the better. Blog posts can be grouped into categories or tagged with what topics the entry touches on. Some blog software allows you to post entries in advance, so you can pre-write many entries and have them show up on a schedule, which may be very helpful.