Online Courses and Tutorials:

1. Coursera: Offers various app development courses, including those from top universities like Stanford and Michigan.

2. edX: Provides free and paid courses on mobile app development, including offerings from Harvard and MIT.

3. Udemy: Offers a wide range of courses on app development, from iOS to Android and cross-platform development.

4. Codecademy: Features interactive coding lessons and projects for app development.

5. Google's Android Developer Training: Offers a collection of free courses and guides for Android app development.

6. Apple's Developer Documentation: Provides comprehensive resources for iOS app development.

Programming Languages and Frameworks:

1. Android Studio: The official Integrated Development Environment (IDE) for Android app development.

2. Xcode: Apple's official IDE for iOS app development.

3. React Native: A popular framework for building cross-platform mobile apps using JavaScript and React.

4. Flutter: Google's UI toolkit for building natively compiled applications for mobile, web, and desktop from a single codebase.

5. Swift: Apple's programming language for iOS, macOS, watchOS, and tvOS app development.

6. Kotlin: An official language for Android app development, fully interoperable with Java.

Design and User Interface (UI) Tools:

1. Adobe XD: A popular tool for designing and prototyping user interfaces.

2. Sketch: A vector-based design tool for macOS, commonly used for app design.

3. Figma: A collaborative design tool that allows real-time collaboration and prototyping.

Development Communities and Forums:

1. Stack Overflow: A vast community of developers where you can ask questions and find answers related to app development.

2. GitHub: A platform for hosting and collaborating on code, where you can find open-source projects and contribute to them.

3. Dev.to: A social platform for programmers and developers to share knowledge and experiences.

Books and Documentation:

1. "The Pragmatic Programmer" by Andrew Hunt and David Thomas: A classic book on software development best practices.

2. Apple's Human Interface Guidelines: A valuable resource for designing iOS apps with a focus on user experience.

3. "Android Programming: The Big Nerd Ranch Guide" by Bill Phillips and Chris Stewart: A highly regarded book for learning Android development.

App Testing and Debugging:

1. Firebase Test Lab: A platform for testing your app on real devices in the cloud.

2. Xcode Instruments: A suite of performance analysis tools for iOS app debugging.

App Monetization and Marketing:

1. Google AdMob: A platform for monetizing mobile apps through in-app ads.

2. Apple App Store Connect: A platform for submitting and managing iOS apps on the App Store.

Online Communities:

1. Reddit's r/appdev: A subreddit for app developers where you can discuss and learn from others in the field.

2. Hacker News: A community for tech enthusiasts to discuss app development and related topics.

3. Indie Hackers: A platform for indie developers and entrepreneurs to share their experiences and insights.

Blogs and Tech News:

1. TechCrunch: A popular source for tech news, including app development trends.

2. Smashing Magazine: Offers articles and resources on web and app development.

These resources cover a wide range of topics related to app development, from learning the basics of coding to design and marketing. Start with online courses and tutorials, and as you gain experience, dive into more specialized tools and communities to enhance your skills and knowledge in the app development field.