Do a search in Google.com for the following terms:
your niche "submit/add link"
your niche "submit/add article"
your niche "submit/add comment"
Obviously, this searches for websites optimized for your niche's keyword, and have the above mentioned terms on their site verbatim.
If you use SEO for firefox (found on seobook.com), you can get in-depth information such as whether the link is no-follow or do-follow, the alexa rank of the site, the pagerank of the site, and more.
There's no reason you can't get good backlinks for your site. Just keep trying.
Good luck warriors.