You could pigtail the neutrals, as Jerry said. But, LISTEN CAREFULLY! You cannot just grab any ol' neutral and pigtail it to any ol' neutral. You can take two neutrals from circuits fed from opposite phases and pigtail them together and then to the neutral bar.
Or, you could tie any two neutrals together and use a #10 pigtail for 15 A circuits, and #8 for 20 A circuits. For the love of God, if you do go this route, heed the warnings above!
Forgot to post that part. Thanks. This makes it a mini-MWBC(sort of). HouseHelper's advice is better(Just make sure the tie bar/strap is reinstalled).