If you have five minutes, here are a few sites you can visit to use your time constructively.
Take quiz on this site to improve your vocabulary and to donate food at the same time.
Very similar concept to the freerice.com site. Sponsored donations.
Small tasks by large number of people can make a big difference. And you can earn some money too.
May be you can help somebody find answer to their question.
Keep your brain sharp by playing games here.