I get this question a lot too. So I started writing down a list of projects. Then I found this one. It is better than what I can come up with. Go ahead and visit the page and pick the projects and work on them.
Below you will find 125 project ideas I have come up with while brainstorming. I have divided them into 10 different topic areas that I think the project may use the most. Keep in mind that a few of these projects could have been classified in more than one topic.