LuaTeX is an extended version of pdfTeX using Lua as an embedded scripting language. The LuaTeX projects main objective is to provide an open and configurable variant of TeX while at the same time offering downward compatibility.
At the TUG 2007 conference in San Diego, the first public beta of LuaTeX was presented. Most of that day was dedicated to the project, its outcomes and its objectives (this project is partly driven by the oriental TeX project). Videos of the conference can be seen here.
There are three closely related projects:
The first two projects result in a collection of OpenType fonts that can be used in LuaTeX and XeTeX. The third project results in a MetaPost library (to be used in LuaTeX) and a version of MetaPost (written in C) that can handle larger quantities and fulfills some long standing wishes of the MetaPost development team.
All these projects report on a regular basis in (local) TeX usergroup journals and at TeX related conferences.
The latest stable release is 0.60 (April 2010) and we regularly post betas (the 0.65 beta is also quite useable). You can fetch the latest binaries for quite some platforms from The ConTeXt Garden or compile them from source yourself.