How To Get It:

Use the installer script to fetch the appropriate package:

curl -L "https://www.opscode.com/chef/install.sh" | sudo bash -s -- -p

Find a package using the omnitruck metadata API:

curl 'https://www.opscode.com/chef/metadata?p=ubuntu&pv=13.04&m=x86_64&prerelease=true'

Note that you need to adjust the query parameters for your platform and platform version. Valid values are described on this page: http://wiki.opscode.com/display/chef/Chef+11+Server+Preview

Install/Upgrade w/ rubygems:

gem install chef ohai mixlib-shellout --pre

Testing:

There are some bugfixes included in this release that we would like your help verifying:

OHAI-455: Some users have reported issues with zombie processes accumulating. I was able to create a low-level repro case and applied a patch to solve it. However, there is a chance that this bug has more than one root cause. If you've had trouble with chef accumulating zombie processes (especially with --fork), I'd appreciate your help verifying that this bug is fixed.
Rubygems 2.0 support: If you're interested in running Chef on Ruby 2.0 or just with Rubygems 2.0, please try this RC with any cookbooks you have that install/update gems.
File/cookbook_file/template/etc. resources: There's a lot of changes, which I've described in a previous thread here and in this gist: https://gist.github.com/danielsdeleo/5732547
The powershell resource has been added to core Chef, so please give it a spin with your existing powershell scripts. In particular, if you have a use case for the architecture attribute, we'd love your help testing. Docs: http://docs.opscode.com/resource_powershell_script.html

Template helpers
Configurable atomic/non-atomic file updates
Automatic restorecon for selinux
Automatic conditional GET for remote_file
remote_file FTP support
Updated ruby in Omnibus packages (will be updated again w/ SSL fix before release). The current RC updates to Ruby 1.9.3p429, which includes many performance enhancements for Windows. Windows users should in particular see greatly improved responsiveness with knife.
Ruby 2.0 and rubygems 2.0 support
Updated knife-essentials with a ton of bug fixes and new features
Added batch file and powershell script resources to core chef
Fixes run lock deadlocks and other file descriptor leaks
Explicit name in metadata.rb is honored
Lots of improvements for Solaris, SmartOS, and friends
Fixed deploy resource getting "stuck" on failed deploys
Lazy evaluation support for resource attributes