I have found many helpful online SEO tools over the years and then lost them due to not bookmarking them or changing my bookmarks around. 

This post contains my all time favorite SEO tools, the ones used on a daily basis.

What SEO tools do you find helpful? Post them in the comments. 
The goals is to create a useful resource for all.

Google

• Google Analytics
• Google Webmaster Tools
• Google Agency Toolkit
• Google Webmaster Central on You Tube   Video answers to your questions

Yahoo!

• Yahoo! Site Explorer

SiteSpeed and Performance Links

• Joomla Performance Site Grader
• Web Wait Time how long it takes your page to load

General SEO Tools

• SEO Browser See what your site looks like to the Search Engines
• SEO Chat Multiple Data Center Search Ranks your site at the different Google Data Centers
• Pineberry SEO page analysis tool Grades pages on important SEO factors

Keyword Tools

• Google Insights for Search
• Google Trends