Amazon S3 - Simple Storage Service

Amazon launched an impressive new storage service. They ask only $0.15 a month per GB stored and only $0.20 a month per GB transferred.

Features:

Write, read, and delete objects containing from 1 byte to 5 gigabytes of data each. The number of objects you can store is unlimited.

Each object is stored and retrieved via a unique, developer-assigned key.

Authentication mechanisms are provided to ensure that data is kept secure from unauthorized access. Objects can be made private or public, and rights can be granted to specific users.

Uses standards-based REST and SOAP interfaces designed to work with any Internet-development toolkit.

Built to be flexible so that protocol or functional layers can easily be added. Default download protocol is HTTP. A BitTorrent (TM) protocol interface is provided to lower costs for high-scale distribution. Additional interfaces will be added in the future.

More info over here.