There are many so-called NewSQL databases, which are designed to scale on par to NoSQL databases while retaining full ACID features.
The competition is getting hard:
Akiban, Amazon Relational Database Service, Clustrix, CodeFutures, Database.com, Drizzle, FathomDB, GenieDB, JustOne DB, Microsoft SQL Azure, MySQL Cluster with NDB, MySQL with HandlerSocket, NuoDB, RethinkDB, ScalArc, ScaleBase, ScaleDB, Schooner, Tokutek, Translattice, VoltDB, Xeround
But how do these compare each other? How can we tell wich is better for our project or advantages and disadvantages of each one, performance comparison, etc?
To be fair, some of them are still on beta and most of them doesn't provide price information on their websites...