Search Engine Optimization is a big topic in the web design industry. There are so many SEO tools out on the web, that sometimes it can be overwhelming.
I've put together a small list of some sites for SEO and a book that I use for reference.
First the book, Building Findable Websites: Web Standards, SEO, and beyond by Aarron Walter. This is a good learner's book and a great reference guide. I think the author mentions just about everything a web designer can do to get the most out of search engines. From creating quality content for humans to read (not just for search engines to get a higher position on the results page) to how to make your awesome splash page (which is a big no-no in the SEO community) indexable for search engines. I recommend this book for web designers who are looking for fast information and need a quick fix for any SEO problem.
Now the SEO tools out there on the web. The first one is at http://www.perfect-optimization.com/web-page-analyzer.php. Here is where you insert of keyword or keyword phrase, the url, and you get results that analyze the Title Tag, Meta Tags, Link Texts, HREF Texts, Head Tags, Bold/Strong Tags, Page Size, IMG Alt Tags and Body Content of your website. The tool lets you know of a percentage you should have of your keyword and how well your site scores on the keyword density. It's free and a simple tool to use for keyword analyzing.
The same site also has a Site Link Analyzer at http://www.perfect-optimization.com/site-link-analyzer.php. This tool is also free. It checks for any broken links and how well your site does with indexing. Links include any kind of links as well.
And last but certainly not least, http://www.seomoz.org/. This is probably one of the best online SEO resources today. My favorite article is on Search Engine Ranking Factors. They go deep into detail about almost every word on a website for analyzation. Check it out here, but I warn you, it's a long read (and well worth it): http://www.seomoz.org/article/search-ranking-factors#f3.
Like I said, this is probably the first SEO site I would go to when having major problems. I highly recommend it.
That's all I have for right now on SEO help, just a book and a few bookmarks that I wanted to share.