Reciprocal Links with Similar Websites: Its important to pick sites that are of high relevance so you’ll not only get links but traffic. Reciprocal linking can be useful from the beginning but don’t overdo it. You can find link partners by emailing them directly or searching through webmaster forums.
Submit your site to Web Directories: This is a pretty monotonous process that can get you several hundred backlinks if you have the time. An alternative would be to hire a manual directory submitter. Here’s a list of web directories you can use. You can also find some blog directories here.
Submit Press Releases to PR sites: A basic press release about your website’s launch can be released to several PR websites, who will distribute it to various online news outlets. A good way to get a free link. I recommend using PRWeb and PRLeap.
Social Media Profiles: There a whole bunch of social websites online which allow you to insert a link to your website on the profile page. Sign up for some of them, preferably using a username and avatar that brands your business or you as a person. This might come in useful when you decide to promote your site via the social website in the future.
Social Bookmarking/Voting Websites. Certain social voting websites like Netscape or Digg are often crawled by search engines and their links do help to get a website indexed. 3spots has the biggest list of social voting and bookmarking websites I’ve seen so far.