1. Coderbyte (coderbyte.com)

This website offers over 2,000 coding challenges that are similar to real-world problems faced by professional programmers. You can practice your skills in front-end and back-end development, data structures, and algorithms. Coderbyte supports over 30 different programming languages and has a library of over 3 million solutions you can learn from.

2. Codewars (codewars.com)

This website provides practice "kata," which are small coding exercises that you can work through to improve your skills. Codewars uses a belt ranking system so you can track your progress as you learn.

3. HackerRank (hackerrank.com)

This is a popular platform for both practicing coding and finding coding jobs. HackerRank offers a variety of coding challenges, tutorials, and resources to help you improve your skills.

4. LeetCode (leetcode.com)

This website is another great resource for practicing coding interview questions. LeetCode offers challenges in a variety of difficulty levels and tracks your progress over time.

5. CodeChef (codechef.com)

This website is a great resource for practicing competitive coding. CodeChef offers monthly coding contests where you can compete against other programmers from around the world.

6. Exercism (exercism.com)

This is a free and open-source platform that provides coding exercises in a variety of programming languages. Exercism also has a strong community of mentors who can help you with your code.