There should be a stable alpha 2 network up soonish. There isn't one right now because it came under attack and, because it was only for testing, didn't have any defenses in place. So MaidSafe are taking a few weeks to implement these ('node aging' for example) and then we'll be good again.
Alongside that they will also create temporary networks 'test 20', 'test 21' etc to test new features (such as 'mutable data') until the next stage which will be Alpha 3.
You can follow the weekly developer updates posted on this forum every Thursday evening, about 19:30 GMT. These describe weekly progress and often announce new test networks.