I just had a party for my DS' 5th.
We got at the local dollar store:
A pack of 12 plastic frogs (could be cute along the lines of the Princess and the Frog, eh?
a pack of dinosaurs
A sampler pack of mini Play-Do
A stack of coloring books (4 for a dollar) and cheap-o crayons
A bunch of stickers
Glow in the dark flowers and butterflies.
I got two mini generic magnadoodles
A giant bubble wand and bubbles
Most were for prizes and then the rest of the little things I chucked into the prerequisite pinyata.
You could also get those feather topped pencils like magic wands (or make star wands with shish kebab sticks and cardboard cut out stars covered in foil to give out), and plastic tiaras (you could make these before hand with foil cardboard and plastic gems or shiny paper) for all the guests mardi gras beads, Ring Pops, stuff like that?
It was really fun.
ETA, the Pinyata eliminates the need for making the party bags, because each kid gets a wee paper bag to collect their loot in (or they can use party hats), and then they can use that to carry any extra prizes, too.