Choosing a window manager is much of a question of taste: at http://www.plig.com you'll find a description of the most common window managers. KDE, the K Desktop Enviroment is particulary noteworthy insomuch it provides a complete desktop enviroment and a full set of applications. At the time of writing it's still in beta phase, this means that many features have not been completely implemented and that the stability still need many improvements. You'll find it at http://www.kde.org.