Just think of something you think is funny or talk to your friends that are into tech either directly or tangentially. A lot of my ideas come from phone calls my Mutual Fund investing best friend.
The same applies for other "utility" stuff – you can create your own flashcards service, which will be super convenient exactly for you, and so forth. So, don't underestimate yourself – software often is good only to some use-cases, not for yours.
I see this with basically everything I use and look at in life: there's always something that can be done better (or better for me at least). Things I'd like to change on my car, things I'd like to change on my house, etc. The problem is lack of time, and too-high barriers to entry. For instance, my car's pretty new and there's some things I wish I could change on it which are really just software, but it's all closed-source and proprietary and completely inaccessible so it'd be a giant project to reverse-engineer it to make even a simple modification. But with open-source software running on a PC, this is a golden opportunity to be able to jump in and learn how others did something, and be able to make your own changes with a relative minimum amount of time getting set up (i.e., not needing to do reverse-engineering). Even writing your own applications is pretty easy these days with Free/open-source compilers, toolkits, libraries, etc. You can do all kinds of things with Python, for instance, and all the tools you need (including the OS) are freely downloadable.
The other day, I was making a website as part of my project. I needed a static site generator. As I looked over the options, I became increasingly of the opinion that they all sucked, and were all far to complicated, especially given my needs (simple blog site: Put together some HTML fragments with templates, and generate an index from another template). I could write something better than this. In fact, I was about to visualize a design when I realized that I had six projects going and really did not need another one.