You can also get a discussion forum for discussion board on the subject of your website. Then, you can go to them and answer all kinds of questions with you. They will allow you to add your website to your signature so that you can promote your website at every post you create.
However, the best use of free advertising is done by singtel advertising solutions. The only problem is that in the form of classified ads where the article never goes away and the forum is stored by the posts, it is also out in the search method, the time limit expires.