Generally speaking, what is the best way to use a mailing list for an adult website (i.e. newsletter which surfers sign up for free), and how ?

I am asking this as I've been building up (slowly) a small mailing list on my website: http://www.israelistrokers.com (the website is still under construction).

Does a small list of about 150 emails addresses 'worth' putting time and efforts into it? (people signed up for it for free). How many subscribers a good mailing list should have approximately before it can start generating income?