Google Dataset Search
Google Dataset Search crawls the structured metadata that publishers add to their dataset pages and turns it into one searchable index. Type a topic and you get results from government portals, universities, data platforms, and research repositories, each with a short summary and a link to the original host.
It is a discovery tool rather than a data store, so you follow the link to the publisher to actually download or query anything. Results carry details like the provider, update date, and available formats where the publisher has supplied them.
For RAG, treat it as a meta-search layer: use it to find candidate sources across the whole web, then check each one's licence and access terms on its own site before you commit to it.
Related sources
AWS Data Exchange
A marketplace for finding, subscribing to, and using third-party data inside the AWS cloud. It carries both free open datasets and paid commercial data products, so you can pull licensed data straight into your AWS workflows without setting up separate transfers.
AWS Open Data Registry
A registry of high-value datasets hosted on AWS and made publicly available, covering genomics, geospatial data, climate, satellite imagery, and more. Over 300 PB of data in total, free to access: you pay only for the compute you use to process it.
Datahub.io
A platform for publishing and finding open data packages: datasets bundled with consistent metadata in standardised formats. It hosts curated collections of widely used reference data, from country codes to exchange rates, ready to drop into a pipeline.
Hugging Face Datasets
The largest open hub for machine learning datasets, with well over 100,000 datasets you can search, stream, and version. Many RAG-ready corpora live here, and its Python library lets you pull data straight into a pipeline in a few lines.