I have not used fluxbox for much time. Openbox is the main reason -i think it 's amazing.
You can install side by side with anything -gnome, lxde, xfce, kde -and then choose from the login screen. It does not come with a panel but i count this as a "+' : almost any panel is available to you. I prefer tint2, a highly customizable panel, but i also suggest xfce4-panel or fbpanel.
As a file manager, i prefer thunar over pcmanfm -again a matter of taste. Nitrogen is a nice solution for selecting wallpapers (feh as alternative). With obmenu, you can edit easily and fast the right-click menu.
Also, take a look here http://code.google.com/p/obkey/
Obkey is the key for editing key-bindings in no-time.
In openbox, you have to edit three configuration files, at /home/your_uname/.config/openbox. One in fact cause obmenu and obkey handling the two of them, thus relieving you. The third file is a simple text file for the autostart applications.
You can check this tutorial: http://community.linuxmint.com/tutorial/view/374
for more info