[DELETED]

For me:
- Traffic Travis
- Market Samurai
- Google Keyword tool
- Affilorama toolbar (shows PR, Alexa rank etc but not as ugly as SEOQuake)
- SEOQuake (when I want more detail)
- IMAutomator (my newly-discovered social bookmarking tool)
- My on-page SEO checklist I created

All 100% free versions

I am using
Google External Keyword tool - to get ideas about keywords
Backlink watch/Yahoo explorer - Analyses competitor links
AMR - Article submission tool (not free)

Article checking tools:
youcanwritearticles.com/tools/keyworddensity/ - Keyword density
spellchecker.net/spellcheck/ - Spell checker
dustball.com/cs/plagiarism.checker - plagiarism checking tool

BookmarkingDemon - For Bookmarking and ping (Not free)

1. Ranking Checker by SEOmoz.com
2. MultiRank Checker by iWebtool.com
3. Fiddler Web Debugging Tool by Fiddlertool.com
4. SEO Analyzer by Sitening.com
5. Strongest Subpages Tool by WeBuildPages.com

Their is several too available according to your requirement . For which tool you are looking for ?

I mostly use Google tools such as webmaster tools, keyword suggestion tool....Google toolbar etc.
Apart from that i am using rank checker, quirk search status etc.

You can now submit your Internet based SEO Tools to this list at the SEO Tool Submission Page. There is a refundable review fee of $5. Only quality SEO Tools will be added to the list.

backlinkwatch , seoquake , webmaster tools , adsense , adwords , and many more tools

There are lots of SEO tools out there. But I will recommend major ones like Google AdWords, Webmaster Tools, SEObook, and backlinkwatch. These are the most recommended ones.

Brad and I just finished up on our new Rank Checker. You can check an unlimited number of keywords in Google, yahoo, and bing.

Here's a free download link for it: Free Rank Checker: Find Out Where Your Sites are Ranked in Google, Yahoo, and Bing! Rank Tracker

and I always like KokChoon's suggestions too. He's got a blog page with a list of the good ones... My SEO & Backlink Tools List

[DELETED]