I want to catalog my favorite shapes, and doing it by computer would be much more convenient and organized.

I once hit a man in Dearborn. Michigan. A hit and run. I hit him and just kept on goin. I don't know if he's alive or dead. But I'm sorry. Not a day goes by i don't see his face.
?? A lot of programme should work. Adobe Illustrator or Photoshop would both do the job. But if you don't have them it wouldn't be worth the cost if that's all you are going to be doing with them. I'm sure you could do it with a basic paint programme using line, circle, and fill tools.