soundcloud and your own site, you can make your own site with worldpress for free (they make money off adds on your site)
then promote yourself on twitter and facebook, add on facebook as friends rappers, like 5 people a day to not get blocked (rappers, not regular people so they don't report you, rappers always want more people to show their music too, you can find them in groups just type in music rap underground ect...) and tweet to rappers that you got beats
you gotta be willing to work to be able to reach out