The Blender Foundation have just released the first test version of the upcoming Blender 2.5 - a HUGE accomplishment as Blender 2.5 is a massive rewrite of many parts of the software such as the user interface (support for multiple windows, completely Python driven, custom keymaps), rendering (volume rendering, much faster raytracing and the beginning of a new interface for external renderers), physics (smoke, new particle system) and a new animation system that aims to make *every* property in Blender animatable.
The naming of this version has caused much confusion over the last few months, but the Blender Foundation seems to have settled on 2.5 for all the test versions and 2.6 for the first 'stable' release. 2.6 is expected to be released 'mid 2010' (SIGGRAPH would seem like a good bet for that). More information about each release can be found in the release logs (see below).
Even if this is 'just' a testing release, this moment marks a milestone for the Blender community. Blender 2.5 is widely believed to be the version of Blender that will overcome the (perceived) notion of being difficult to use by users of other 3D applications. That, combined with the powerful new feature set may well be its ticket into a much, much larger user community.
Congratulations to everyone involved with your hard, hard work!