The red, green and yellow bits in sort of 'Lucky Charms' type shapes are pellets. So are the brown cylinder-shaped things.
Here's Petsmart's listing for Nutriberries showing the prices:
http://www.petsmart.com/product/index.j ... lInUS%2FNoYou can save several dollars if you order them on Amazon.com, and they're eligible for free shipping. The four-pound tub lasts about two months with my flock.
http://www.amazon.com/Lafeber-Company-N ... 0002ARFO2/http://www.amazon.com/Lafebers-Classic- ... 0002567WS/Nutriberries should be counted as pellets not seed, so you'll need a seed mix too. I don't have a favorite seed mix brand because they all seem to have so many fillers, and I make my own seed mix using only seeds that I know the birds will actually eat. If you wanted to do this you could buy a basic parakeet mix like this one:
http://www.amazon.com/Kaytee-Supreme-Fo ... 0002AQN8G/and add some sunflower and safflower seed to it. I also add hemp and buckwheat to my seed mix but these seeds are harder to find.