Mono 2.10 incorporates three months worth of work and brings Google Native Client support, a new profiler engine, faster socket stack, an improved parallel framework, unified MonoTouch/MonoDroid run-time support, a new C# compiler back-end, a VB compiler, improved Mono OS X support, WebMatrix.Data database API support, and F#, IronRuby, and IronPython are all packaged for Linux now.
For a full list of details on this major Mono update, see the release notes.
Miguel and his Mono team have also released their first preview of Moonlight 4, which seeks to implement Microsoft's Silverlight 4 under Linux and other platforms. Though it doesn't fully implement the SIlverlight 4 specification and only with this preview release does it now round out the SIlverlight 3 features.
Changes here include new rendering features, a new rendering pipeline, GPU acceleration support, a platform abstraction layer, and much more. The GPU acceleration actually sounds quite interesting as it leverages Gallium3D, with fall-backs to OpenGL when Gallium3D is not available. More on this will potentially come later (en route to the Munich airport so this post is brief).
See more on Miguel's blog or at Go-Mono.com.