Nope. Just one.
Though you can combine the rods with actual feats you have.
Yeah, just one rod use per spell.
One rod per spell. But, if you have a quicken rod or the quicken feat, you could use two rods in a turn. One on the standard action spell, and one on the quickened, swift action spell.
This is how my group has been interpreting the rods as well, but I have been reconsidering it lately. What I am wondering is with only two hands how do you hold and activate a quicken rod to cast a spell, then someone hold and activate a maximize rod to cast a spell as you standard action. If you have a rod in each hand how do you perform the somantic component of the two spells? Plus getting a item out of storage (even your handy haversack)is a move action. We have always played that putting it back into storage would be another move action. So, assuming you can perform the somantic component with just one hand and that you start the round with the quicken rod out, I still do not think you could use two metamagic rods in one round. Swift action to cast quickened spell, move action to put rod in haversack, move action to get maximize rod from haversack, standard action to cast maximized spell. I suppose maybe if you dropped the quicken rod you could do this, but no one want to drop a rod. I also suppose you could craft a rod that has both quicken and maximize in it to avoid switching rods, but the cost would be 1.5x for the second power.
Metamagic rods are already powerful (and cheap!) enough that they don't need any further rule-bending to make them even moreso.
YMMV.