Everyone is used to Google's AdSense system offering relevant ads instead of providing static banners. This system not only affects the acceptance of advertising on blogs, but also enhances the user experience. Being able to access relevant products or content by one click is certainly a much more attractive and modern way of offering ads.
Could a similar system be also built for free blog-to-blog linking? I guess there are many blogs out there dealing with almost the same topics from time to time, and I think it's a pity that there is no automated way ( i know of ) to link these blogs based on the post contents. While a hard restraint for such a service to work would be that it is free and easy to customise, many bloggers focusing on their readers would embrace such a system. Once again, free and without any commercial background.
Edit: I guess someone's done some cool work here, the plugin is called Ping Crawl and links to related posts and also pings them. Nice! Edit, 2: Ping Crawl to be quite uncontrollable and since it actually just looks at your tags, it's not working well. Though text analysis is certainly hard to do, it's the only way, I'm afraid.
This is another one of my ideas, and I'd be really glad if I could only realise one of them. If you want to help me out, please please please contact me.