I use Pinterest. I have boards with photos of finished and unfinished quilts, 2 or 3 on which I'm exploring quilt ideas, eg inspirations for the bright pink quilt that I'm making at the moment, and others for tutorials and techniques, quilts I like and art quilts. And all my other boards on subjects that interest me are also potential inspirations.
https://uk.pinterest.com/annesthreads/
I also have a notebook in which I jot down anything I need to remember, eg supplies needed, maching settings, ideas for quilts.