Make GTK applications look like Qt 4 ones
There are two themes available which look the same under both toolkits (GTK/GNOME and Qt/KDE): "QtCurve" is provided via packages gtk-engines-qtcurve and x11-themes/qtcurve-qt4, "Oxygen" is part of KDE 4.x, its GTK counterpart is provided via package x11-themes/oxygen-gtk. KDE themes can be configured via KDE's System Settings under "Appearance" in tab "Style". In order to configure the theme of GTK applications from within KDE's System Settings, install kde-misc/kde-gtk-config to get a new tab "Gtk Config" under "Appearance".
If you click to view the menu and notice that there is nothing legible, you need to install some fonts. Some common choices are media-fonts/corefonts, media-fonts/ttf-bitstream-vera, kde-base/oxygen-fonts and media-fonts/dejavu.