Apart from using the web 2.0 sites, it can be difficult to get backlinks from other webmasters. One way that I have found to be effective is to develop a free Wordpress theme (with your keyword rich anchor text in the footer, linking back to your site) and submit it to all the free Wordpress theme directories.
You don't need to be a coder to create a wordpress theme, you can cheaply outsource this. Once you have your theme, you can submit it to the various free Wordpress theme websites on condition that your link remains intact. Everyone and their dog has a blog nowadays, and a decent free Wordpress theme has the potential to bring your site loads of backlinks.