Lisp has been used to build a wide range of applications across different domains. Here are some popular applications that have been developed using Lisp:

1. Artificial Intelligence (AI) and Machine Learning : Lisp has a strong association with AI and has been widely used in AI research and development. The language's expressive power, metaprogramming capabilities, and support for symbolic computation make it well-suited for building AI systems. Lisp was used in the development of early AI systems, such as the expert system language "CLIPS" and the natural language processing system "ELIZA." Lisp dialects like Common Lisp and Scheme continue to be used in AI and machine learning applications today.

2. Symbolic Mathematics : Lisp's support for symbolic computation and its ability to represent mathematical expressions as data make it a natural choice for building symbolic mathematics systems. Applications such as computer algebra systems (CAS) and numerical computation libraries have been implemented in Lisp. Notable examples include Macsyma, which was one of the earliest CAS, and Maxima, an open-source descendant of Macsyma.

3. Language Processing : Lisp has been used in the development of programming languages and language processing tools. Lisp's metaprogramming capabilities and homoiconicity make it suitable for implementing compilers, interpreters, and parsers. The widely-used programming language Common Lisp itself is often implemented in Lisp. Additionally, the programming language Racket, which is used for teaching and research in programming languages, is built in a variant of Lisp.
4. Robotics and Control Systems : Lisp has been employed in the field of robotics and control systems. Lisp's flexibility, interactive development environment, and support for real-time programming have made it useful in developing robotics software and control algorithms. The Open Robot Control Software (ORCOS) framework, for instance, provides a Lisp-based environment for developing robotic control systems.

5. CAD/CAM Systems : Lisp has found applications in computer-aided design (CAD) and computer-aided manufacturing (CAM) systems. Lisp's extensibility, domain-specific language capabilities, and support for geometric operations make it a suitable choice for building CAD/CAM software. The CAD system AutoCAD, for example, initially used a Lisp-based programming language called AutoLISP for customization and automation.

6. Games and Interactive Entertainment : Lisp has been used in the development of games and interactive entertainment applications. The game development company Harmonix, known for creating games like Rock Band and Dance Central, used a Lisp dialect called Scheme for game development. Lisp's ability to rapidly prototype and experiment, along with its support for AI and simulation, can be advantageous in game development.

These are just a few examples of the many applications built in Lisp. Lisp's flexibility, expressiveness, and metaprogramming capabilities have made it suitable for a wide range of domains and problem domains.