For Winamp you should be able to find an Winamp Plugin description on the Winamp site, together with a "SDK" (a simple, cutomizable plugin example). It's really not a big deal, you need to generate a DLL that exports a set of functions required by Winamp. This is why I asked you what program you need to develop plugins for, they are highly application dependent. A Winamp plugin is a good place to start. If you can't find an example just PM me and I'll send one of my own to you.