Maybe you’ve heard that it’s good to have a blog on your website – that it brings more visitors. Want proof?
I have a fun little website – a labour of love – that I’ve been growing for 10 years now, the Nova Scotia Photo Album. It started out as a wedding gift on a floppy disk in 2000, and now it has its own domain and more than 1000 photos of Nova Scotia organized with captions, mostly taken by yours truly.
Look what happened after I installed a WordPress blog on the site in November 2008. The graph below shows traffic to the site from Google, according to Google Analytics.

The blue line is traffic to the site from July 6, 2008 to June 20, 2009. The orange line is for the same period a year before, 2007-2008.
Note that this isn’t the traffic to my blog, it’s the traffic to the site itself, just from Google. You can see that traffic started going up around Christmastime and kept rising.
The curious thing is that traffic to the blog itself does not account for the difference! Here’s the traffic to the blog homepage (the only page with significant traffic) for the same period:

In this period, no more than 90 visitors saw the blog homepage in any week, yet Google alone was sending 200 extra visitors a week to the site – people who wouldn’t have shown up if previous trends had continued.
Other sources of traffic did not change significantly over that time period.
Furthermore, it seems that the traffic was coming for a wide variety of long tail keywords as I was blogging about them.
Conclusion: the mere existence of a WordPress blog on a website, if you’re updating it regularly (I have averaged twice a week) can increase your site’s status with Google. The rest of my site got more traffic just because a blog was there, even if people weren’t visiting the blog.