SplogReporter.com was created for "good willed" bloggers to report splog in an effort to help to clean up the blogosphere of splog.
SplogSpot is a splog blacklisting service. You can help build the splog blacklist by submitting splogs.
From JenSense:
If you see a site violating the AdSense terms, you can now file an anonymous spam report that will get to the quality team for checking. To file a report, you simply go to the page that is showing AdSense ads and click on the "Ads by Google" (or "Ads by Goooooogle") link. In the form on the next page, include the term "spamreport" and put in a short reason about why you feel the site is violating the AdSense terms or policies. You can also enter your own email address, if you wish, then click submit.
Blogger says that "When a person visiting a blog clicks the “Flag?” button in the Blogger Navbar, it means they believe the content of the blog may be potentially offensive or illegal".
They go on to say "For more serious cases, such as spam blogs or sites engaging in illegal activity, we will continue to enforce our existing policies (removing content and deleting accounts when necessary)".