o Directory submissions.
These sites offer lists of niche directories to submit your link to:
http://www.directoryarchives.com
http://www.isedb.com

o News feeds.
PR Web and others offer free and paid services to give you a chance to secure links in news articles about your company.
http://www.urlwire.com/
http://www.prweb.com/

o Become an authority site and get sites to link for you for free. Creating content people want to link to.
Example, http://www.searchenginewatch.com

o Leave testimonials.
Example, see the footer area (very bottom of the page) of: http://searchenginelowdown.com/

o By donating to charities and non profit organizations.
Many sites allow you to donate to their cause and they will give you a link on their site.

o Volunteer web development services.
Many non-profit organizations need a web presence but cannot afford professional web design services. Offer them for free in exchange for a credit at the bottom of their pages.

o Making tools and content that make people bookmark the site.
Example, the link popularity check tool at:
http://www.marketleap.com/publinkpop/default.htm

o Giving things away for free.

o Ask for links from suppliers and friends in your industry.

o Write articles and submit them to similar websites.