Xxkb is a simple XKB keyboard mapping switcher. It maintains
an active keyboard mapping on a per-window basis. An optional
small icon is displayed in each window to indicate the selected 
keyboard mapping. You can click this icon to switch between
mappings in addition to being able to use the key combination 
specified in the XKB configuration.

Xxkb works with virtually any window manager.

WWW: http://www.tsu.ru/~pascal/other/xxkb/