Ruby on Rails 2.1 and the MagLev Ruby virtual machine
First, 2.1 looks like a great update: I have not seen any compatibility problems with 2.0 that could not be instantly fixed. The named_scope (has_finder) changes look good for organizing database queries, and I especially like the way they nest. I have not tried using the new gems dependency functionality yet but this looks very useful when deploying applications to fresh servers.
The news about the large performance boost using MagLev looks interesting, but I will reserve my enthusiasm until the project is further along and I can try running it myself. I find myself reverting from coding in Ruby back to Common Lisp or Java to get around performance issues, so a much faster Ruby runtime environment sounds good. Ruby is such a slow language, that there is plenty of room for improvement.