As curiousgeorgej said, you don't need xbindkeys for this. Openbox itself can manage keybindings. You might find the official documentation useful as well: http://openbox.org/wiki/Help:Bindings
Please note that if you use LXDE, you will need to edit the lxde-rc.xml file, and not the rc.xml file that Openbox normally uses and that will be referred to in most documentation.
To launch a terminal with the keybindings Ctrl T, you would add the following to your (lxde-)rc.xml in the <keyboard> section:
Code:
<keybind key="C-t">
<action name="execute">
<command>urxvt</command>
</action>
</keybind>
Replace urxvt with whatever terminal you prefer to use.
You might also be interested in this post I wrote some time ago: http://urukrama.wordpress.com/2008/0...x-keybindings/