Search engine optimization is a complex and dynamic subject. Fortunately, there are many websites which have valuable information, lots of practical tips and discussion on latest trend. Following is a list of select Net resources that can be very helpful.

Keyword Density

High search engine ranking requires your pages to maintain optimmum word depth and keyword density. Keyword density is the ratio of a keyword or keyphrase to the total words (depth) on a page. Many search engines today are measuring keyword density as a factor in assigning relevancy ratings to web pages. If your keyword density is too low, your page will not be rated high in relevancy. On the other hand, if your keyword density is too high then the search engine may penalize you for "keyword stuffing". Optimizing Keyword density is considered an important aspect of search engine placement. A density of 1% to 7% is generally considered good.

Keyword Density Analyzer

Keyword density and word depth calculator

Keyword Selection

Wordtracker - Provides list of most commonly used keywords in search engines

SpellWeb
Use SpellWeb to make quick checks on possible variants or synonyms and compare popularity. For example, you could check how often 'money' is used compared to 'cash', etc.

Meta Tags

Meta Tag Builder
This site creates meta tags for your pages. All you need to do is to feed it with information about your site.

Meta Tags Generator<
Like above, generates meta tags for your web-pages. You need to submit information about your site

Free META Tag Analyzer and META Tag Help This site analyzes your meta tag sets and warn you if there is any mistake or the tags are not sufficiently spider friendly. Helps you with possible solution

Back to Basics - Meta Tag Tutorial

Meta tags explained by JimWorld secrets of search engine ...

Meta Tags Generator
Generates meta tags for your web-pages. All you need to do is to submit information about your site