I only use google analytics regularly. Apart from that, the DP keyword suggestion tool when getting my meta descriptions and tags setup on a new forum....

I used to know a great site that would check PR on every page of your site free quick and easy but i think it went dead

I usually use google analytics.

It depends.
We like the SEO CMS, SEOTOASTER, which enables you to execute SEO best practices from the get go. It puts you on the right track.
Then you can connect to Seo Samba which integrates with the Google Tools (Optimizer, Analytics etc) but mainly executes SEO implementation (deeplinks, 301 re-directs, link sculpting, smart URLs, ....) Great results, that's what we want.

Google Keyword Suggestion Tool - This device is for investigating keywords, their search numbers, as well as finding out many of variations and alternative keywords.

these are some of the tools which i use:

Search Analytics Tools - establish your marketing goals and establish a baseline for where you are at right now.
Keyword Research Tools - discover the keywords your customers are searching for right now.
Competitive Research Tools - see what keywords your competitors are targeting.
PPC Tools - buy important keywords and track the results to understand how well they convert, which helps you focus you organic SEO strategy on the most profitable keywords. Save money using these free Yahoo! Search Marketing & Microsoft ad Center Coupons.
Link Analysis Tools - start building your link profile and track your progress compared to competing websites.
Search Engine Ranking Checkers - determine how effective your marketing is by watching your search engine rankings improve.
Blogs are a great SEO tool, even if everyone is passing on reading the article written, Google never does. Now, with that being said, one also needs to note that although Google never passes the articles by and continually indexes keywords found in the articles, companies still believe that the articles written need to contain good content.

FF plugin, "SeoQuake", for PR checking, backlinks checking, etc. For the the keyword search, I'm using Google Keyword Suggestion Tool. Up to now, I'm not yet using any paid tool for SEO purposes.

Google keyword suggestion tool
Google Analytics
Google toolbar
Google Webmaster Tools
Msn Webmaster tools
Yahoo Webmaster Tools

Most of the time i use plugins for firefox like:
searchstatus -show page rank, alexa, compete and mozrank for every website i browse
seoquake -it good for google search engine to show web searches websites stats in same window
firebug -to solve and find mistakes on my websites

Other than that i every day login in to google analytics and check results.

I use....
Google Adword
SEO Spy
SenSEO
Search Status 3.1