I've been using Uberchord for a few years by now and it's just amazing. It's all about chords, rhythm and songs. This is no child's game, though, you actually learn how to play. The recognition works for most of my guitars and is borderline crazy, even showing me if I put a finger on the wrong fret. It won't let you just play anything and still pass. They have courses library (they call it learning path) and a pretty large catalog of popular songs. I wish they had solo training, but all in all, highly recommended.
Apple iWork - iWork is an office suite by Apple.
Fretello - Duolingo for learning how to play guitar
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.
Justin Guitar - Over 750 completely free guitar lessons!
Bit.ai - Bit is a smart real-time document collaboration platform for teams to create interactive documents, manage digital content and track document insights.
Guitar Pro 7 - Create, play and share your tabs