Justin's Piano Buying Tips
Where should I rent my violin? - Kenneth Stein Violins - great violins, great price. Don't buy anything if you are a beginner. Much better to rent and upgrade as you grow in size.
International Music Score Library Project/Petrucci Music Library - Amazing resource for all public domain scores (ie, most classical music).
Musicnotes.com - excellent resource for downloading and printing popular music scores.
https://www.spotify.com/us/ - great online library for streaming music. Imagine iTunes being free, and that's pretty much what spotify is!