Over at the Datastax blog, Tyler Patterson created a tutorial for getting started with Cassandra Cluster Management (CCM), which creates multi-node Cassandra clusters on the local machine. Here's a slice of the introduction, you can check out the whole thing below.
[CCM] great for quickly setting up clusters for development and testing, and is the foundation that the cassandra distributed tests (dtests) are built on. In this post I will give an introduction to installing and using ccm.
CCM, A development tool for creating local Cassandra clusters, by Tyler Patterson