For me its :
Bandcamp, Youtube, No1 Music, Soundcloud, Reverbnation, Facebook.
And you need to really work at getting it all up to scratch and presentable. I have done all the driving endless amounts of traffic to my sites but in the end those views are fake, and yeah they look good, but they dont do a whole lot at the end of the day as no-one is actually listening to you.
The best thing to do is to network yourself. And work HARD. Dedicate one night a week, ( one whole day preferably ) to emailing similar members on Youtube. ( Search *Your genre* Filter " Most Recent " ) and then go on to subscribe to those people, comment on some of their videos and build a rapport with them by messaging them and talking about each others music. By the end of the day you'll have several genuine friends, more connections, and will even be featured on several other Youtube channels if you do well. Also offer to collaborate with anyone you think you will mesh with.
I tend to email record companies and in my case, game developers, about once a month. I give them a link to my bandcamp page ( used to be Youtube, deleted it though ) and explain who I am, what I'm about and what I'd like to offer them.
Very often I still offer free tracks to online flash games. It means these guys come to me when they need anything and I have repeat business from about 4 indie game developers right now. My name is featured on each game and I'm hoping to get my name everywhere possible. One day you never know, someone might pick up on that, email me, and new business comes.
In many markets spreading yourself too thin is a terrible idea. But if you have a set website with albums and playlists people can list instantly, it doesn't hurt to get yourself out there. Out everywhere.
NOTE: Personalise everything. Put thought into each message and forum post. Don't just use ToolTube and send everyone the same generic message. Being in the game myself, I used to spot these messages instantly in my Inbox and delete them. Its nice to use the persons name and actually comment on their own featured music , and be genuine.