Here is an interesting idea from a tip offered by Dave McInnis of PRWEB–
Locate a press release on PRWEB that is relevant to the subject of your blog and comment on this release on your blog. Then setup a trackback to the release.
If you make an interesting comment and have a decent blog (spam blogs will not benefit from this most of the time), the press release owner may approve your trackback which will appear as a comment on his release. This trackback can setup a cool incoming link to your blog. These trackback links are not set as ‘nofollow’ at the time of writing this post.
Warning: Do not use this to to spam PRWEB as that will result in everyone losing the benefit.