Collection of Free SEO and Social Media Tools

Twitter Tools

TweetVolume (enter a few phrases and see how often they appear on Twitter): http://tweetvolume.com/
TweetScan: http://tweetscan.com

Google Tools

Google Keyword External Tool (keyword suggestion tool): https://adwords.google.com/select/KeywordToolExternal
Google Insights for Search: http://www.google.com/insights/search/
Google Trends: http://www.google.com/trends
Google Search Based: http://www.google.com/sktool/#

SEO Tools

Backlink checker: http://seopro.com.au/free-seo-tools/link-checker/
Search Engine Spider Simulator, Backlink Anchor Text Analysis, Keyword Density Checker, Website Keyword Suggestion, Alexa Ranking Tool: http://www.webconfs.com/
Backlinks pointing to your website: http://backlinkwatch.com/#
Keyword Competition(analyzes the first 5 results), Keyword Density Tool, Backlink Checker: http://www.justsearching.co.uk/seo_tools.html
SEO Analysis Software: http://spydermate.com/
Type a keyword or phrase and get the top 20 competitor pages analysis: http://nichewatch.com/
Search Engine Optimization Analysis Tool: http://www.seoworkers.com/tools/analyzer.html
Website Grader: http://websitegrader.com/

Social Tools

Check your presence on social Networks: http://www.bizshark.com/

SEO Moz Tools

TermExtractor – This tool analyzes the content of a given page and extracts the terms that appear to be targeted at search engines. It applies certain weights to HTML elements and other on-page factors to determine what it thinks is a targeted term.
http://www.seomoz.org/term-extractor

TermTarget – By analyzing the frequency and location of keywords throughout a page, the Term Targeting tool assigns a letter-grade to a page that represents how well certain keywords are targeted.
http://www.seomoz.org/term-target