virtualbox.org

I'd like to run a script in a Linux guest just before the VM is paused, and another script just after the VM is resumed. Does anyone know if this is possible? If it is, I'd expect that it would depend on the Guest Additions.

Virtualbox does not provide any hooks to perform pre-tasks, so you would need to handle this yourself outside of Virtualbox via a script or something like that.
As for the actualy guest part, yes you would need the guest additions and you could use guestcontrol in vboxmanage or the Virtualbox API.