Here are a few sites to check out:

http://vran.org/about-vaccines/specific-vaccines/influenza-vaccine-flu-shot/flu-vaccine-%E2%80%93-think-again/

http://www.activistpost.com/2013/01/5-reasons-why-ill-never-get-flu-shot.html

http://articles.mercola.com/sites/articles/archive/2011/10/31/flu-vaccination-epa-safety-limit-for-mercury.aspx

http://www.medicinenet.com/flu_vaccination/patient-comments-859.htm

These are only a few sites that speak out against the flu vaccine. Some simply have comments from those who have received the vaccine and suffered adverse effects and others have some factual information. Ultimately, it is up to you to determine what is useful knowledge. Happy searching!