Free directories
Almost every topic has a directory that accept free submissions. Submit your site there. Do a search on your favorite search engine for "yourkeyword directory", "yourkeyword links" etc.
 
Submit to the major link directories
Google seems to add weight to the websites that are listed in DMOZ and Yahoo directories. If your site will be accepted in DMOZ, soon it will appear in the Google directory and in hundreds of DMOZ clones out there. If you've got budget, submit your site to the Yahoo directory. If you don't have the budget, try the free submission (don't expect too much though). For non-commercial sites a submission to Zeal.com could be worth the time you need to understand their submission guidelines. 
 
Links Quality
Quality, on topic links work best. Don't waste your time by submitting your site to FFA pages and by spamming guestbooks and forums - this is not a long term solution and those links seems to count less and less in the last time.

The secret to get a lot of good one-way links for free
Write quality content for your website. Provide some free services that everyone would love. Work really hard and with passion and you will wonder how many people will link to you. Not because of the link exchanges or PR, but because they like your website. At last, that is what the web is about - the links from some sites to other.