One of the things that bugs us all about Google is how to contact them about new features, bugs, help, downtime, etc. I've complied a quick list of services/products they offer and the links you need to contact Google about the service. Also, I've included links for the Google Group and Help center related to that specific service/product.

Google Help A – Z: google.com/support/bin/static. ...

Adsense
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Contact Us: www.google.com/adsense/support ...
Google Group: groups.google.com/group/adsens ...
Help Center: www.google.com/adsense/support ...

Adwords
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Contact Us: adwords.google.com/support/bin ...
Google Group: groups.google.com/group/adword ...
Help Center: adwords.google.com/support/

Base
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Contact Us: base.google.com/support/bin/re ...
Google Group: groups.google.com/group/base-h ...
Help Center: base.google.com/support/

Blog Search
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Help Center: google.com/help/about_blogsear ...
Email Support: blogsearch-supportgoogle.com

Books
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Email Support: books-supportgoogle.com
Help Center: books.google.com/support/

Calendar
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Contact Us: google.com/support/calendar/bi ...
Google Group: groups.google.com/group/Google ...
Help Center: google.com/support/calendar/

Checkout (Buyer Help)
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Contact Us: checkout.google.com/support/bi ...
Help Center: checkout.google.com/support/

Checkout (Seller Help)
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Contact Us: checkout.google.com/support/se ...
Help Center: checkout.google.com/support/se ...

Earth
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Contact Us: earth.google.com/support/bin/r ...
Google Group: groups.google.com/group/earth- ...
Help Center: earth.google.com/support/

Gmail
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Suggest a Feature: mail.google.com/support/bin/re ...
Contact Us form: mail.google.com/support/bin/re ...
Google Group: groups.google.com/group/Gmail- ...
Help Center: mail.google.com/support/

Google.com Search
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Contact Us: google.com/support/bin/request ...
(Same form is used for Images.google.com)
Help Center: google.com/support/

Google Groups
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Contact Us: groups.google.com/support/bin/ ...
Google Group Help: groups.google.com/group/Google ...
Help Center: groups.google.com/support/

Maps
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Contact Us: maps.google.com/support/bin/re ...
Google Group: groups.google.com/group/Google ...
Help Center: maps.google.com/support/

News
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Contact Us: news.google.com/support/news/b ...
Google Group: groups.google.com/group/google ...
Help Center: google.com/support/news/

Scholar
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Add your website for inclusion: google.com/support/scholar/bin ...
Help Center: scholar.google.com/intl/en/sch ...

Toolbar (Firefox)
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Contact Us: google.com/support/firefox/bin ...
Google Group: groups.google.com/group/FFTool ...
Help Center: google.com/support/firefox/

Toolbar (Internet Explorer)
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Contact Us: google.com/support/toolbar/bin ...
Google Group: groups.google.com/group/IETool ...
Help Center: google.com/support/toolbar/?hl ...

Video
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Contact Us: video.google.com/support/bin/r ...
Google Group: groups.google.com/group/Google ...
Help Center: video.google.com/support/

Just a note, Please don't abuse the contact us forms before you take the time to find a solution in the help center and/or Google Group related to the product/service your inquiring about.

Nice list, that permalink will be used quite often to send others to.

All these are available using a simple google search and the links are available in the help center of each google service. But that doesn't mean they're useful and someone Google actually answers your question.

google.com/search?q=gmail+cont ...
google.com/search?q=add+site+t ...
google.com/search?q=google+map ...

Not all of the Contact Us links was easy to find by going to help center of the specific product. Thats why I originally created the list so I wouldn't have to hunt for it.