IS THERE?!
Are you kidding, there's an onslaught of WP SEO plugins.

All-in-one SEO is quite popular.

So are these:
20 of the Best SEO Plugins for WordPress

It isn't terribly different from optimizing any other sort of site (:

Ok, Just make sure your site is optimized for post/page titles.

I usually set the plugin to use ONLY the exact post or page title for the title tag.

So instead of the default:

MY WEBSITE | MY POST TITLE

I have it as:

MY POST TITLE

Of course, my post title is the exact keyword that I am targeting.

The majority of your SEO work should be spent on backlinking though, unless you are in a very low-competition niche/keyword, the on-page SEO won't do much on it's own.

Hope this helps.

-Dave

If you don't know how, you can hire an SEO expert to optimize you site. In that way you will surely be on top of Google ranking. I can help you if you want.

Wordpress is very authentic web 2.0 sites. It has given me good back links.

Don't get too caught up with all these "SEO Plugins." I use them myself, but they're no magic bullet. They help you do things like create Title tags, Meta descriptions (which don't even boost rankings anyway), and other things like that, but these are all things you could have done manually, anyway.

If you want to rank, forget all the little plugins and themes and learn how to build high quality backlinks to your homepage.