As previously reported, Google has put out seven new videos about various kinds of webspam. Last time, we looked at one about unnatural links from your site. This one is about unnatural links to your site.
Once again, it's pretty basic stuff, as Google is including these videos in its documentation about webspam.
"If you've gotten this message, it basically means that we have seen enough low-quality or spammy links to your site that it's affected our opinion of your entire site" Google's Matt Cutts says. "We don't like to take action on sites. We prefer not to, but we have to protect users."
Google essentially wants you to contact the sites that are linking to you, and have them take care of them (whether that means removing them, nofollowin them, redirecting them or whatever), and submit reconsideration requests.
If that doesn't work, use the Disavow LInks tool. As we recently discussed, not everyone thinks this is working well enough.