I think that the forum and gridmail features are getting used well enough but I think that nodes are where usage is really way low.
What I would love to see:
1. Each big corp hires a "Gridmaster" to keep their nodes up to date and secure.
2. All those NPC run businesses offer contracts to create nodes for them (It can be as simple as the companies name, brief description, location information and contact information). Contracts would also be offered if their node needs to be updated (new contact info for example), or recovered after being attacked.
3. Characters (especially non-mixers) cared about what their node said or looked like. Even if it was just a matter of deleting it. This can also be good business for deckers and help establish contacts.
4. Companies and Characters (when appropriate) start storing sensitive information on the Grid as comments. We all know that nodes can be hacked but that's why you hired and trust your Deckmaster to lock down this info.
This can all be done without needing a single line of code changed - just a mentality shift on players part. Of course, the initial hiring of deckers by corps and companies to get nodes started at all would require more GM time and that might be why this hasn't happened anyways.
If I could add one thing to the Grid right now, I think that it would be access control on grid nodes. The ability for the decker to set who can view a node and who can not (of course a decker can override this using cracking). Maybe even let them set who can edit a node (without having to crack it) and who can not as well, though I am not so sure about this one.
I think that this would encourage groups to store information on the grid and having that would motivate deckers a bit maybe.