One observation that I've read countless times now is that blogs are great for SEO because Google loves fresh, unique content. It seems a bit hackneyed but it's certainly still true.

And one way the factor manifests in the SERPs is that you do seem to get a bit of a lift in your rankings for various keyword searches in the period immediately after your latest blog post has been indexed by Google.

Here's an example: I have a local blog about my home city called The Real Perth Blog. It's been going a year or so now and currently sits in the top half of the first page for searches for "Perth blog". If I haven't updated it for a while, it's usually fourth on the list. But if I add a fresh post to it, which is then indexed, it tends to go up to the third position, where it is now.

Sure, this seems like an insignificant lift. But it can have substantial traffic benefits over time. This is because the number of clicks you tend to get goes up considerably for each position your site rises when it's already near the top of page one. So, it's yet another reason to update a blog frequently if you can find the time.