Conveyor Belts and Objects

So, it's very simple to make a conveyor belt that moves an actor, but can one be made to move an object such as barrel or stimpack?

Yes, see Freedoom's E1M3 for an example.

I guess I should have mentioned I'm trying to achieve this effect in ZDoom.

I'll open up Freedoom and take a look.

The Scroll_Floor action should do the work for you. You can code it in ACS or assign it to a line. Even the relatively well known "train" WAD, seen here, uses that effect to scroll objects like trees so that you're given the impression of being on a moving train.

EDIT:
Here's a conveyor belt example set on MAP01 with just a couple scripts that do all the work for you. One script begins the scrolling of the conveyor belt and also endlessly (silently) spawns barrels. The other script removes any barrels that reach the end of the conveyor belt and is tied to a line I placed there. As a result, it seems as if you're looking at a conveyor belt carrying an endless supply of barrels. I hope this helps you out.

Thanks Chubz, only you'd go through the effort of making an example wad.