When I spoke about link building at Pubcon I mentioned getting links by finding broken links. I thought I would write a post that talks about this in more detail.
When doing link research on your competitors you can find broken links. You can take advantage of this by sending an email to the site owner and letting them know about the broken link and how your site provides the same content. If you don't have the content create it. Tell them that your site not only has the same content but you have more detailed content.
Another approach is to write a program that activity searches out broken links. Once you have a good list you go through it and send the same type of email.
Sometimes you might find websites that are no longer updated. Try to get a hold of the owner and see if you can take the site over if it is hosted on a free or paid service.
I've just taken on a client who's launching a niche information site, and whilst researching their niche have found that two large and very well-linked sites were discontinued in the UK as of November. Lots of the places I want links from link to one or the other.
I haven't tried it yet but I think this is could be a dynamite way of getting quality links; you're in the site owner's 'good books' because you're helping them so they're pre-disposed to at least checking your site out.
I've also come across people linking to - domains that have fallen into the hands of domainers - domains that have been suspended by the web hosts
and again I'm hoping that the success rate here will be quite high.