As announced on the community site, Windows Workflow Foundation (WF) Beta 2.2 is available here.
A very important point to note: You can not install this on top of an installation of the February CTP of WinFx. So, if you have WinFx installed you will have to uninstall it, all the pieces and parts, in order to install Beta 2.2. If you are focused on a solution that only leverages WF, and not WCF or WPF, and want to upgrade to a newer version of the bits which are closer to the version which will be released, this is the path for you. If you are building a solution that leverages additional WinFx technologies, you will want to stick with the February CTP.
The install of Beta 2.2 contains all of the components (see below) of a WF install, and is titled the "Microsoft Visual Studio 2005 Extensions for Windows Workflow Foundation Beta 2.2." That's a mouthful. For Beta 2.2, this is the only thing that you need to install. A summary of the changes are contained here.
On to a completely different topic. I've also gotten some questions about why the WinFx install contains what seems like 3 different installs. The simple answer is that there are really three components to WinFx (and thus, applies to WF).
So, three pieces: runtime, SDK, designer, and now you know why they are there.