SynthMaker is a graphical programming environment for creating digital sound and music. The latest Windows Beta version 0.9.1a is free to download and features a drag and drop GUI for easier creation of soft synths and digital filters. You can export your creations in VST or VSTi formats for use in other applications. There’s an online introductory guide and a user support forum. Further documentation is currently being developed.
If you’re not sure what Beta means check this definition first.