I've started a
blog on my site, partially as a way of making the page's content change regularly (to keep the SEs happy) and partially because I like writing about stuff! I don't know how many of my clients (prospective or otherwise) will be reading it though, although this isn't something I'm aiming to get them to do.
A client that I'm working with now is toying with the idea of starting a blog/news page on his upcoming site, I don't know exactly how he feels about it yet though. It wasn't my idea (it was the SEO guy who suggested it) but I don't think it's a bad thing for him to do, not only for search engine visibility but also to give the site more of a human edge.
I'll post back here when I hear more about it
-Sam