We've scoured the internet for good services that do not breach the Spotify TOS and offer good, organic promotion for your music. The easiest way to do that is to be put into playlists, email lists, DJ groups, and broadcast on popular social media channels.
These services charge a nominal fee, but if you truly believe your music is good, it's worth the fee as you should gain back your money from the royalties anyway!
This first one below is the premium service! Your song is put into popular, genre specific playlists, email lists, blogs, and social media.