Updated 5 Jan 2006
I've added a new sourcecode download from L.D. Blake who kindly sent me a great little splitter library called "Easy Split". From the readme:
"EasySplitter is a custom control, in library format, that can be used with Pelles C to implement a very simple splitter window. With EasySplitter you create a splitter bar as a windows control that you can size, move and stylize like any other windows control. All mouse capture and window drag operations are handled internally by the control itself."