ClockWise Orange is a fractional delay based plug-in. With its multiple controls, it lets you perform many sound transforms which are well adapted to electroacoustic music. More than most traditional plug-ins, it is very convenient in live or interactive situations, since many interesting phenomenon appear while you interact with one or many of the parameters.
The provided version is free and fully functional, and includes a reference manual and a large set of example presets. Contact the author if you want a copy of the source code.