Here is another one - persistent memcache:
[quote]People like memcached because it represents a practically boundless place to easily cache data, at very low cost and with predictably stellar performance. No schemas, no tables, no sharding, no normalizing, no tuning. You want to put something in memcached, you put it in there. Why put it in two places!?[/quote]

Membase
gigaom com/2010/06/23/open-sourced-membase-joins-nosql-party

Pretty [url=http://www.techcrunch.com/2009/12/10/stealth-startup-relaxed-raises-2-million-from-redpoint-ventures-for-couchdb-support/]cool[/url] and worth checking out:
[quote]For those who are unfamiliar, CouchDB is a free open source indexable document database server which uses Javascript as a query language. CouchDB is designed for the reporting and storage of large amounts of semi-structured, document oriented data, unlike SQL databases which store and report on very structured and correlated data.

CouchDB is part of the rapidly growing [url=http://en.wikipedia.org/wiki/NoSQL]NoSQL[/url] movement, which is schema-free and focuses on adding horizontal scalability to databases. Major companies already use NoSQL database systems including Amazon’s Dynamo, Facebook’s Cassandra, and Google’s BigTable. Other NoSQL-related projects include Project Voldemort, Hypertable, VPork, MongoDB, Apache’s Hadoop and more.[/quote]

The concept of cloud definitely requires new, horizontally scalable type of storage - I recall even the MS folks who promoted Azure admitted that it doesn't work very well with MySQL, and really is meant to use their block storage system, which of course requires a totally different architecture and mindset, not to mention throwing away all the SQL-based legacy apps...