Social bookmarking has become very popular with people able to bookmark for others sites that are interesting. Some people see this as an opportunity to submit multiple links for search engine optimization purposes to build up backlinks. In some cases this is a great strategy, but not all sites offer a direct link to a website. In some cases redirects are used as well, which has no benefit to your website.
Another form of promoting your site is through classified ad systems where you can post an ad to the category of your choice, control the content and in some cases post multiple links to the site.
With some ad systems, direct links are offered and eventually these sites have their pages indexed in the search engines. If the ad post is categorized and related to the theme of your site, this may be a great alternative to building links to your website