CtrlBrk has released an alpha version of VstBoard, a free, open source, VST host and plug-in for Windows. Its main purpose is to allow fast switching between setups and was primarily designed to be used as a guitar multi-fx.
CtrlBrk says that it's still in development so don't expect too much - it may be unstable!
* Multiple setups per file.
* Fast switching between setups.
* Runs standalone or as a plugin.
* Free (unrestrained) audio and MIDI routing.
* Some basic scripting capabilities.
* Undo/redo, your mistakes, endlessly.
* Customizable interface (dockable windows, custom colors, zoom, plugins windows size and position).
* Localized : EngRish and French.
* Other useless stuff.
You can download it here http://vstboard.blogspot.com/