Google Cloud Storage supports the same API as Amazon S3, so the S3 special remote can be used with it. Here is a configuration example:
git annex initremote cloud type=S3 encryption=none host=storage.googleapis.com port=80
Thanks to jterrance for the original tip. --Joey
I just found the "Interoperable access" thing. The instructions from Google (linked in previous comments) are not perfect.
After step 4 click "Google Cloud Storage", then at the bottom you have a heading called "Interoperable Access" where you have to activate it for this project.
Then it appears at the bottom of the left hand menu.
According to the last comment, and this page: * https://developers.google.com/storage/docs/migrating#keys
there's supposed to be a "Interoperable Access" menu option, something I can't find. Note that both the previous comment and this page refers to Googles old Developer Console.
I can find a few things under "APIs and Auth" => "Credentials" under the heading "Public API access", but no matter what kind of key I try to create I can't get anything other than an API key. No secrets here, and no "Show"-button for newly created keys.
Another thing worth mentioning is that these API keys I'm seeing do not like described in that first link in this comment. It's much longer, contains both upper- and lowercase and also contains dashes.
This looks very valuable - Google are offering a free 5GB up until 2013 June 30th
Sign in here[1] get your credentials here[2] under the section “Interoperable Access” (Source[3])