If you have an unused domain name just sitting around, I've got a good tip for a free authority backlink. If you host all your websites on the same hosting account then all your domain names share an IP Address. This means when you link between your sites the search engines will recognize your domains as all being on the same server. This will give you less link juice than having a completely separate hosted domain linking back to you. So, what you can do is sign up for a free blog at Tumblr and opt to use your own domain name. Just update the nameservers to Tumblr and you have a new website on a separate hosting account. Best part is, Tumblr is a high authority website so sharing an IP address with them will give your Link even more juice. Now you can post blogs, pictures and other media with links to your websites for bonus link juice. Do some social bookmarking to your new Tumblr blog to get tiered links all pointed to your site. As a bonus you start getting PR to your new Tumblr blog's domain name. This is what I have done with my website http://www.enterscope.com and I have a tumblr blog at http://www.ntrscp.com that links back.
I forgot to mention that stuff you post on Tumblr ranks high on search engines so that's another plus.
I think your idea make sense and it worth trying if someone large number of websites hosted on the server..I tried tumblr blog in past it worth using for back links and get traffic.