Get More Fans - a very informative and up-to-date book for learning the ins and outs of the music industry as an independent musician.
indieflow - a music management software company for independent musicians and labels. Streamline your music projects, royalties, distribution and promotion through an easy to use web app.
chartmetric - all-in-one platform for artists and music industry professionals, providing comprehensive streaming, social, and audience data.
Bandsintwon for artists - create a profile, add and promote your upcoming tour dates, and even sell tickets directly to your fans, plus reach new ones and promote your music. You can also track your tour dates and manage ticket sales, and keep in touch with your fans through your artist profile. there are also informative industry webinars you can tune in to.
Killed By Desk - a weekly podcast for DIY musicians
Sound Exchange - focuses on royalties for your recording (mechanical rights)
Spotify Playlists Page on Reddit
Toneden - social media marketing platform
Show.co is one as well
Sidedoor - online ticketed streaming service for shows
Hype Machine - a blog you can use to search bands that sound like you to see what publications have covered them. This is useful for targeting your press releases.
ari's take - a music business education and artist advocacy company focusing on empowering musicians to have successful careers in the new music business.