Social bookmarking sites are very good source of getting backlinks, specially digg & stumbleupon are most effective. U can also use reddit, fark, propelar, mixx etc.
here are many advantages of article submissions,and one of them is to Increase the no. of backlinks of your website (which is one-way incoming links towards your site).
Depands a lot on what's your final objective? the qty or the quality. If you want traffic qty expanding, try social bookmarking,or just keep on doing white seo. It's a hard job,but you have no choice but continueing with what u r doing now.
Try Link bait!
It refers to anything on a website that encourages links from other websites. It can include content, online tools, downloads, or anything else that another site owner might find compelling enough to link to. Link bait is important because most search engines use backlinks as a major factor in determining ranking.
Posting helpful responses on other peoples' relevant blogs will get you quick backlinks but don't overdo it and ensure you contribute to the blog - (read it first), this can help.
Be careful to find the right balance. Whilst getting backlinks is great, be careful to follow the rules. If you are suspected of using black hat techniques then your site will be banned from the SERPS. However, if you follow natural techniques and don't try to cheat the system then you will be fine.
So, as others have mentioned:
Social Bookmarking
Post in Forums
Article submission
Post a Blog, and comment on other blogs.