There are several online courses and resources available that can help in developing memory, concentration, and focus. Here are some options to consider:

1. Coursera: Coursera offers a range of courses related to memory, concentration, and focus. “Learning How to Learn” is a popular course that provides practical techniques for improving memory and concentration.

1. Udemy: Udemy offers various courses on memory improvement and focus techniques. Some recommended courses include “Memory Mastery: Learn To Build A Healthy Memory” and “The Complete Focus Mastery Course – Brain Concentration.”

1. SuperMemo World: SuperMemo World is an online platform dedicated to improving memory and learning skills. They offer courses, materials, and software designed to enhance memory retention and concentration.

1. Lumosity: Lumosity is a popular brain-training platform that offers a variety of scientifically designed games and exercises to improve memory, attention, and cognitive abilities. It provides personalized training programs based on individual needs.

1. MindTools: MindTools provides a collection of practical resources, including articles, videos, and worksheets, to enhance memory, concentration, and focus. They cover techniques such as mnemonics, visualization, and time management.

1. Memrise: Memrise is an online platform that focuses on language learning but also offers courses to improve memory and concentration. They use spaced repetition techniques and interactive exercises to enhance retention.

1. TED-Ed: TED-Ed is an educational platform that hosts a series of short, animated videos on various topics. They have engaging talks and presentations that explore memory techniques and strategies for improving focus.

Remember to review user reviews and ratings, as well as the course content and instructor qualifications, before enrolling in any online course to ensure they meet your specific needs and goals.