The rules for grappling aren't exactly great, are they? Oh, well.
Say I want to maintain a grapple. It's a standard action, so I can't use a Full Attack.
Spending my standard action leaves me with a move action. I can't move, being grappled, but can I use it to anything else worthwhile?
Yes, you can use your Move action for whatever you want, as long as it isn't actually moving* and as long as it doesn't require two hands to do it.
*if you're the grappler and make a successful check to maintain your grapple, you can choose to move at half speed and take your opponent with you - this doesn't even require your Move action (and you still can't actually move on your Move action); this is part of the Standard action to maintain the grapple.
Get Greater Grapple, use move action, profit. :)