By Telephone or FAX
Visit this page to see all offices of Google with details address, phone numbers and FAX.
Google offices with address: http://www.google.com/intl/en/about/company/facts/locations/

Send Feedback to Google
You can send feedback as well as can give suggestions to Google.
Send feedback: http://www.google.com/tools/feedback/

Contact Google's press team
You can send feedback as well as can give suggestions to Google.
Email: press@google.com

Reporting security issues
If you want to report any security incident to Google then report it to following email.
Email: security@google.com

For toolbar problems and feedback
If you want to report any toolbar problem then report it at the following page.
Toolbar problem: http://support.google.com/toolbar/bin/request.py?contact_type=problem

If you want to give any toolbar feedback then give it at the following page.
Toolbar feedback
Gmail related feedback: http://support.google.com/toolbar/bin/request.py?contact_type=feedback

If you want to send any Gmail related feedback then send it to following email
Email: gmail-feedback@google.com

Adsense related support
If you want any support related to Adsense then send it to

Email: adsense-support@google.com

Google news source
If you want to include your website in Google news source then mail to following.

Email: source-suggestions@google.com

Share your success story
If you have a great experience with a Google products and you like to share it then share it in the following page.

Share your success story: http://www.google.com/contact/success.html

Source: http://www.stalyfblog.com/2012/06/how-to-contact-google.html

Thanks for sharing.