With this DSP/Effect Plugin for WinAmp you can load the VST Plugins (standard plugin interface for professional audio effects) directly in WinAmp. There are also several good and free VST Plugins out there (http://www.betabugsaudio.com)
On initial selection of this as the active dsp plugin and then going to the config option i was left wondering what this was going to be like. Once you're used to the rather quirky ui, the vst plugins are easily loaded and from what i could see work well. Shows promise.