Here’s an interesting online, open source journal recently created for works in (you guessed it) mathematics. Kind of an old link, but still interesting.. basically those works that haven’t made it into a major journal can be published here, along with the reasoning for non-publication and an author’s defense.
This brings up an interesting question (which is discussed at the link as well) about whether it will look bad if one has published here, since of course that meant the piece was not up to some sort of peer review standards. Would it be better to not publish at all or go this route? What are your thoughts?