Websites

In order of recommendation...

WaniKani

Focus: kanji
Style: lessons/reviews (SRS*)
Cost: subscription (after level 3)

Bunpro

Focus: grammar
Style: lessons/reviews (SRS)
Cost: subscription (after 30 days)

KameSame

Focus: kanji
Style: reviews (SRS)
Cost: free
Notes:

JapanesePod101

Focus: general (but particularly listening)
Style: lessons (video/audio)
Cost: subscription (some free content)

Satori Reader

Focus: reading (and listening)
Style: reading/reviews (and listening)
Cost: free/subscription for full features

Duolingo

Focus: general
Style: lessons/reviews
Cost: free (you can pay for useless add ons)
Notes: Duolingo doesn't have the best reputation for Japanese, but it's improved and is fine for some light learning/revision

* 'SRS' means spaced repetition system