Yeah it is possible, but it's not so convenient.
There's a red trunk in the Guild office that all players can put items into for others to take out. It seems so far that you can put any sort of item into it.
This office is the only time you can do this though.
I had a Cook over yesterday and we were getting wrecked in the Lava Cave. I was out of potions and he wanted to give me some food he'd made for health but you can't
You can't save online, but going into the trunk forces the game to save, so that's a nice way to get around that.
The trunk also gets around bounties too. As only one player can cash one in, I've been putting half of what I get in the trunk for others so they don't miss out.