I've seen lots of idea/tutorials for pincushions, including more than a few mason jar pincushions. This was one of the first crafty things I tried that I found on a blog.
There was kind of a problem though. Most of those people had actual mason jars (with the two part lid). I, however, had a pasta sauce jar that was kind of a mason jar except the lid was all one piece. Not quite as good. So I improvised because I had to have one of those mason jar pincushions.