Here's a (far from complete) list of front-ends available for Csound.
CsoundGUI is a cross-platform, versatile GUI which is part of the standard Csound distribution. It implements most configuration features of Csound.
This is a simple java program to play csd files. It is included in the standard distribution.
Also part of the main Csound tree (though not available in all distributions), Winsound is cross-platform FLTK port of Barry Vercoe's original front-end for csound.
A convenient front-end for windows with syntax highlighting. You can get it at the WinXsound Front Page.
A convenient front-end for windows with syntax highlighting. You can get it at the Flavio Tordini's Home Page.
More than a front-end for the Mac at MacCsound Page.
Cabel is a graphical user interface for building csound instruments by patching modules similar to modular synthesizers. Cross-platform, written in Python. At http://cabel.sourceforge.net/.
Composition oriented front-end written in Java. It's interface is much like a digital multitrack, but differs in that there timelines within timelines (polyObjects). This allows for a compositional organization in time that seems to me to be very intuitive, informative, and flexible. Get it at: Blue Home Page.
This front end which is part of the main csound tree, is contained in some standard distributions. Apart from file editing and csound execution, it allows csound to be used as a VST plugin in suitable hosts.