I often get a bit confused as to whether certain symptoms are related to the flu or a cold, and the site is a good resource on this topic. It also has info on vaccines and what ages of people should get one. The older I get, the more I think about getting vaccinated for the flu; honestly I have yet to get the flu vaccine myself, but my grandma is a very health 95 year-old, and she swears by it and is always trying to convince me to get it, so one of these years I think I am going to follow up on her advice.
Vaccine Hub is actually a pretty comprehensive resource in general regarding vaccines for other illnesses such as whooping cough. Where I live, whooping cough has been making a comeback, and I did get immunized against it earlier this year. If you are looking to do any international travel, I would also recommend Vaccine Hub as a starting place for some ideas about immunizations you may need--they have useful maps as well as interesting articles.
For more useful and relevant information on the flu for people in all parts of the world, check out this link: http://www.vaccinehub.com.au/diseases/influenza.