(1) URL tagging tool - This Google Analytics URL builder tool will help you to fill in the form information like Campaign Source, Campaign Medium, Campaign Term, Campaign Content and Campaign Name and click the Generate URL button for the tagging URL.
The tagging URL will look like http://www.seoaday.com/?utm_source=blog&utm_medium=post&utm_campaign=example
Tool URL - http://www.google.com/support/analytics/bin/answer.py?answer=55578
(2) Rich Snippet tool - This Rich Snippets Testing Tool will help to check your structured data markup and it shows how Google display your URL in search results.
The Rich Snippets will look like below,
Tool URL - http://www.google.com/webmasters/tools/richsnippets
(3) Crawl URL tool - This tool helps you to submit pages to the Google Index and which doesn't require ownership verification. So you can submit any URLs that you like.
Tool URL - https://www.google.com/webmasters/tools/submit-url
(4) Page Speed Service tool - This tool is for requesting access to the Google Page Speed Service. If your site is too big with loads of information and you like to speed up your website then you need to give it a try. This service is a limited service.
Tool URL - https://docs.google.com/spreadsheet/viewform?hl=en_US&formkey=dDdjcmNBZFZsX2c0SkJPQnR3aGdnd0E6MQ&ndplr=1
(5) Page Speed Online check tool - This tool helps to measure the website performance and provides optimization suggestions for developers.
Tool URL - https://developers.google.com/pagespeed/
The page Search Engine Optimization (SEO) Help... got an overall Page Speed Score of 90 (out of 100)
Apart from the above tools, there are many widely used common tools like Google webmaster tools, Google keywords tool, Google insight, Google trends and Google traffic estimator.
If you find any new Google tool, feel free to mention.