Have you seen a site without links? There will not be a site without links. If a site does not have a links pointed to it we can say that site is almost a dead site. If we do not have out bound links it wont matter but we should have inbound links. Even a site with best content isn't worth much when there are no inbound links to it.
So, after building a website it is important it appears high in search engine rankings. The best way to get good targeted visitors are search engines. Many visitors to the web site come from search engines. The most popular search engines use link popularity in their ranking algorithms (how sites are evaluated). Improving link popularity moves sites up in the ranking and a high position in search results. Back links play a very important role in the search engine ranking. You also must have quality links to make the search engine take notice of your site. No quality links means you will never get a high ranking.
It is important to keep in mind the quality of the site before getting links from it.
1. If your link is placed on a page with hundred other links it would not give any value.
2. If you can not reach the page where your link is placed probably do the search engines. Hence your site receives no value from such link.
3. It serves no value if you get link from a site which has been banned by google.
Also avoid getting links from sites
1. Which have hidden links / text on it.
2. Link farms - sites which link to every site indiscriminately.
It would be useful to get links from the sites with similar content. For ex: If you have a ringtones site getting links from other ringtone, mobile, music etc sites would be useful.
Although one way links are best it would also help to have relevant reciprocal links from the similar sites. You link to my site and I link to your site. That's what reciprocal link exchange is. It is best to have themed resource pages to do link exchanges. Each page should be on a particular theme. Then you can put the out bound links according to the theme or you can also give links on the content page as it is most useful to the users who visit your site.