Best free resources for learning English?

Strong English opens doors to scholarships, jobs, and study abroad. Where should someone start for free?

What I'd recommend:

• BBC Learning English — structured and free.
• Reading anything you enjoy in English, even simple news, builds vocabulary fast.
• Language-exchange apps to practise speaking with real people.
• Change your phone's language to English for daily, gentle immersion.

What worked for you? Especially keen to hear low-data options for those on mobile connections.