Cassandra is supported by most of the major programming languages. Most of these libraries are open source, and rigorously tested. The libraries provide fail-over support and connection pooling ability. The latest driver lists can be viewed at http://wiki.apache.org/cassandra/ClientOptions. Here is a list of some drivers that support CQL 3:
Java: You can find the DataStax Java driver at https://github.com/datastax/java-driver and the Hector Java client at http://hector-client.github.io/hector/build/html/index.html
Python: You can download the drivers for Pythons such as Pycassa at http://github.com/pycassa/pycassa and the DataStax Python CQL driver at https://github.com/datastax/python-driver
Node.js: You can find the Node.js driver Helenus at https://github.com/simplereach/helenus
PHP: You can find the Cassandra PDO driver at http://code.google.com/a/apache-extras.org/p/cassandra-pdo/
C++: You can find the LibCQL C++ driver at https://github.com/mstump...