There are several databases that have been integrated with the Nostr network, including but not limited to:
1. Wikipedia: A free online encyclopedia that contains information on a wide range of topics.
2. OpenAI: An artificial intelligence research laboratory consisting of the for-profit corporation OpenAI LP and its parent company, the non-profit OpenAI Inc.
3. Wolfram Alpha: A computational knowledge engine that provides answers to factual queries by computing the answer from structured data, rather than providing a list of documents or web pages that might contain the answer.
4. Google Knowledge Graph: A knowledge base used by Google and its services to enhance its search engine's results with information gathered from a variety of sources.
These are just a few examples, and there may be other databases that have been integrated with the Nostr network as well.