Openbox can run inside the GNOME, KDE, or LXDE desktop environments, giving you all the power and features of Openbox alongside everything these desktop environments have to offer. Options to run Openbox inside of these desktop environments are provided by default in the Session Type menu when logging in graphically, as seen in Figure 1. Choosing the "GNOME/Openbox" or "KDE/Openbox" option will log into the respective desktop environment with Openbox replacing the default window manager.
If you use lxdm, make sure it is version 0.3.0 or newer. Older versions had a bug which interfered with sessions other than LXDE.
See Using Openbox in GNOME for further tips and assistance.
Using Openbox without a desktop environment (The lightweight approach)
By default, a third "Openbox" option is provided in the Session Type menu when logging in graphically, as can be seen in Figure 1. This option will run a more lightweight Openbox session without any desktop environment or session manager.
When choosing this option, the autostart file is executed before launching Openbox, so that you can run any applications you want to start alongside Openbox and set up the environment as neccessary. Openbox comes with a default autostart which sets up an environment for both GNOME and KDE applications to run properly in (if you have them installed), as well as providing support for SCIM language input. See the autostart documentation for more details on setting it up.
To have a taskbar on screen, install and use a panel program like gnome-panel, pypanel, perlpanel or fbpanel. Our list of programs to use with Openbox lists a number of such programs.