On the Internet there are many sites that are made on a "free classifieds". It all depends in this situation only the content of your links. So with the help of search engines you need to choose the most appropriate message Board and then search for the desired subject category. As a rule, to do this, it is enough to have an account on the website (register), however, sometimes it is not even necessary. Commonly on these portals it is better to post links about selling anything.
If the content of your links has a wider application (i.e. it does not sell), then, to distribute it, you need to register for a free massive portals. Suitable accounts on sites like http://www.livejournal.com or http://www.vkontakte.ru. There you can freely upload any information (including the link) on his personal page. Censorship is minimal. Therefore, if your link does not violate the rules of the site does not contain any malicious software, then it can be easily spread, and then just share the link with your users.
For even wider distribution links need to be placement thereof on forums or communities. The massive forums/group can be absolutely free and effective advertising. However, the censorship in this case is stronger than on its own page. Therefore, the content of the url and description must be correct and thematically similar to the place where you want to place the link.
On the websites, it is not specialized in, harder. To put a link, you must contact the website. To do this it is usually not difficult, since almost any website there is a section "contacts". If your link is appropriate to the site thematically, there is some probability that it will be placed for free (or under other conditions: link exchange, etc.).