The following are links to persons and applications that are and have been particularly useful in my learning path to a composer of music.

Learn music:

Tracy Rose, piano teacher: http://musiclessonsanywhere.net/
Jon Brantingham, composition teacher: http://www.artofcomposing.com/

Opinions about music:

http://aarongervais.com (composer)

http://www.contrapunctus.com (composer)

Software:

MuseScore 2: https://musescore.org/en/
Sound fonts: http://www.synthfont.com/soundfonts.html
EastWest: http://www.soundsonline.com (look for "Composercloud")
Pianoteq: https://www.pianoteq.com/
Garritan: http://www.garritan.com/products/
Audacity: http://audacityteam.org/
SynthFont2: http://www.synthfont.com/