Recently I participated in the Problogger's 31 Days to Build a Better Blog project for my personal blog. It was a very enlightening project that I highly recommend for any blog (either business or personal that is at 6 months old. It is not something that you have to complete in 31 days. Think of it as 31 lessons to refine/enhance/improve your blog.
The cool thing is that Darren Rowse of Problogger has put together the 31 tasks into a neat notebook which also includes bonus material that is not on his website.
I plan on using this workbook as an audit for my blogs every 6 months and I think it is useful enough for you as well!