I have found listing startup in web directories help bring more users. This massive list of web app directories put up by Justin Mcgill really saved me a lot of time.
He had made this list way back in 2014 and some of the links were not working when I tried. So I put up this list of all working links of web directories, along with some more that work today. I have informed him as well so that he can keep his list updated.
Let me know if you find any relevant web directories missing. Or if any are not working. I ll update this list.