As I mentioned a few minutes ago in my story about Google's new manual spam action viewer - Google has documented all of the manual actions a site may receive for spamming their search results.
Here are the eleven documents from Google on these manual spam actions:
- Manual Actions
- Cloaking and/or sneaky redirects
- Hacked site
- Hidden text and/or keyword stuffing
- Pure spam
- Spammy freehosts
- Thin content with little or no added value
- Unnatural links from your site
- Unnatural links to your site
- Unnatural links to your site—impacts links
- User-generated spam
With that, Google produced a total of nine videos, I believe only seven being new videos, on these manual actions.
Here are all nine videos:
Does Google take manual action on webspam?
Hidden text and/or keyword stuffing:
Thin content with little or no added value:
Unnatural links from your site:
Unnatural Links to site:
Unnatural Links to site - impacts links:
Every SEO should make time to read all those documents above and watch all these videos.
Forum discussion at Google Webmaster Help.