This Rails application provides a resource to practice writing kanji and can be found live at Heroku. By creating an account you can make your own lists of kanji to practice with (but only if the kanji are already in the database). Kanji are organized by category (jōyō, jinmeiyō, and hyōgai) and level: Jōyō grade, JLPT level, or WaniKani level.
Meanings and readings for kanji characters are from WaniKani and Jisho. All the awesome stroke-order diagrams come from the open source project: KanjiVG.