Ok. I'm going to list off some ideas for projects. You will have to determine if any particular idea is good enough to include in a portfolio. These aren't creative ideas. They likely already exist. Some are way too advanced while others are simplistic.
I will recommend to post any project you make to github and make a github project page for it. Explain in as much detail as possible how you made it, how it can be improved etc. Document it.
If you pick an advanced idea, setup a development roadmap and follow it. This will show some project management skills.
Another piece of advice for those who are design challenged. Use different front end frameworks and use different themes for those frameworks to provide appealing designs without looking like yet another bootstrap site.