Carefully Choose to Whom You Link To
Websites that you link to create your neighborhood of websites if you will. If websites that you link to are known to be spammy websites by the search engines then the search engines may also think that your web site is spammy. Link farms would most likely be included as spammy websites.
What you want to do is link to websites that have good content and websites that are reputable. If you choose to link to high quality websites then web surfers will associate you as a high quality website also.
It's important to remember that sending people to other websites is not sending customers away from your site since they are going to leave at some point anyway. What is more important is creating a friendly neighborhood of useful information so you viewers will come back to you time and time again.