NoSQL databases are non-relational databases that are designed to handle large amounts of unstructured or semi-structured data, such as JSON documents. Some of the main NoSQL database services include:

1. MongoDB: A document-oriented NoSQL database service that is designed for high scalability and performance. It uses a BSON (binary JSON) format for storing data, and it’s known for its ease of use and horizontal scalability.
2. Amazon DynamoDB: A fully managed NoSQL database service offered by Amazon Web Services. It’s a key-value store database service, optimized for high performance and scalability.
3. Cassandra: A wide-column NoSQL database service that is designed for high scalability and performance. It is known for its ability to handle high write loads and its support for data replication across multiple data centers.
4. Redis: An in-memory key-value store NoSQL database service that is known for its high performance and low latency. It is often used for caching and real-time data processing.
5. Couchbase: A document-oriented NoSQL database service that is designed for high performance and scalability. It is known for its support for complex queries and its ability to handle both structured and unstructured data.
6. Apache HBase: A column-family NoSQL database service that is designed for high scalability and performance. It is based on the Hadoop Distributed File System (HDFS) and it’s often used for real-time big data processing.
7. Riak: A distributed NoSQL database service that is designed for high scalability and fault-tolerance. It supports a key-value data model and it’s often used for high-performance, distributed systems.
8. Cosmos DB: A globally distributed, multi-model NoSQL database service offered by Microsoft Azure. It supports document, key-value, graph, and column-family data models.
9. Elasticsearch: A distributed NoSQL database service that is designed for search and analytics. It’s based on the Lucene library and it’s often used for full-text search and real-time analytics.
10. Firebase Realtime Database: A cloud-hosted NoSQL database service offered by Google Firebase. It’s a real-time, document-oriented database service that is optimized for mobile and web application.

These are some of the main NoSQL database services, but there are many other options available as well, and choosing the right one will depend on the specific use.