Anki is a program which makes remembering things easy. Because it is a lot more efficient than traditional study methods, you can either greatly decrease your time spent studying, or greatly increase the amount you learn.
Anki vs SuperMemo opinions
Anki is under active development, and has a large user community. There are many videos on YouTube showing how to use it, and giving tips.
RemNote is the note-taking tool that gives you memory superpowers. It automatically generates flashcards from your notes and figures out the optimal time to practice each flashcard so you don't forget what you've learned.
Have fun while learning a foreign language with Memrise. The more you enjoy learning, the more (and quicker) your skills will develop. This is why entertainment mixed with real-life, relevant content is at the very core of the Memrise language learning experience.
Mochi is a cross-platform desktop tool that lets you take notes and make flashcards using markdown, then study them using spaced repetition.
Spaced-repetition app, the best for scientists and coders. With rich formatting, with images, with code formatting, with formulas, with multiple flashcard types. Entirely free, open-source.
Learning with Texts (LWT) is a free tool for Language Learning by reading & listening to texts, saving & reviewing vocab. Prerequisites are an installed LAMP/WAMP/MAMP (local web server & database) software and a modern web browser.
Mnemosyne (named for the Greek goddess of memory, Mnemosyne) is spaced repetition software developed from 2003 until the present. The software is similar to SuperMemo, commercial software developed by Piotr Wozniak.
AnkiApp is a simple, efficient, flashcard app that lets you study at your own pace, whenever you have time. Study sessions are as quick as 1 minute or less. It works on phones, tablets, and desktop browsers, and synchronizes automatically between all your devices.