I recently purchased a plugin that analyzes my copy, lets me know what the search engines think about what I've written, lets me know what I should change to draw in more traffic, and provides tips on best SEO practices.
Scribe works with WordPress if you’re able to fill in a custom title tag and meta description for the post or page. While Scribe was originally developed for the Thesis Theme for WordPress, it also works with the free All in One SEO plugin, the hybrid theme, and the headway theme.
I have found that many of my posts were too short, and often I forgot to put a key word in the title tag. If you are using the All In One SEO plugin it's a piece of cake to make sure the title and description are the right length to maximize your SEO efforts without getting to “keyword happy.”
It is a subscripton model (not a single price). The pricing starts at $27 a month for 30 evaluations, and goes up to $97 a month for 300 evaluations. You can use it on unlimited websites. You can try scribe for free for 30 days.
After using it on my Logical Weight Loss Podcast, I am #2 in Google for the phrase “weight loss podcast.”