No SQL and Open source

The list goes on and on.

There are so many open source no sql databases these days that its difficult to choose one unless you have specific requirements.

I never thought the open source database systems would be part of so many applications.

Here is some I know:

couchdb

mongodb

leveldb

simpledb

mariadb

memcachedb

ravendb

geniedb

extremedb

tokutek

googlesql

queplix

eyedb

sterling

AvocadoDB

Voltdb

There are so many and many of them you can find @ http://nosql-database.org/

some more here:
CrowdDB
Shark