Akka: Akka is a powerful toolkit and runtime for building highly concurrent, distributed, and fault-tolerant systems. It is based on the Actor model and is widely used for building reactive applications.

Play Framework: Play is a web application framework that is built on top of Akka and Akka HTTP. It is designed for building scalable and reactive web applications, providing features for both Java and Scala developers.

Lift: Lift is a web framework for building interactive and real-time web applications. It emphasizes security and scalability and is known for its Comet support, which enables server-push functionality.

Spark: Apache Spark is a fast and general-purpose cluster computing system for big data processing. While Spark itself is written in Scala, it provides APIs in multiple languages, including Scala, for distributed data processing.

Scalatra: Scalatra is a lightweight, micro web framework for building RESTful web services. It is designed to be simple and flexible, making it a good choice for creating web APIs.

Finagle: Finagle is a protocol-agnostic, asynchronous RPC (Remote Procedure Call) system for building high-concurrency services. It is used for building scalable and resilient microservices.

Cats: Cats is a library that provides abstractions for functional programming in Scala. It offers type classes, data types, and functional programming utilities to help developers write more modular and composable code.

Slick: Slick is a functional-relational mapping (FRM) library for Scala that allows developers to work with relational databases in a type-safe and functional way. It provides a DSL for database queries.

Doobie: Doobie is another database library for Scala that focuses on compile-time safety and type-safety when working with databases. It is designed to work seamlessly with functional programming principles.

Scalaz: Similar to Cats, Scalaz is a library for functional programming in Scala. It provides a wide range of functional abstractions and utilities for writing more expressive and robust code.

Finch: Finch is a library for building HTTP services in a purely functional style. It is designed to be lightweight and composable, making it a good choice for functional web service development.

Circe: Circe is a JSON library for Scala that provides encoding and decoding of JSON data in a functional and type-safe way. It is often used in combination with HTTP frameworks for handling JSON data in web services.

These are just a few examples of the many frameworks and libraries available in the Scala ecosystem. Scala's versatility and compatibility with Java also mean that it can leverage a wide range of Java libraries and frameworks, further expanding its capabilities for various development tasks.