I use Wunderlist to keep track of both large and small tasks. For a long time, I kept my trusty notepad with a running list of to-do's, ready to jot down new items as they were thrown at me. That system had a number of fail points. Wunderlist allows me to have my list available no matter where I am. I have also used it to share lists with other users to keep projects in sync and everyone on the same page with what needs to be done.