For birthday invitations, make personalized dollars for free at Festisite.com. Upload the honoree's photo, print the bills, and write the party details on the back.
Print free images from NewMoney.gov (look under "redesigned currency").
Back each printout with card stock, cut around the portraits through both layers, then glue them together, sandwiching a toothpick in between. Jot facts on the flip side.
Stick the toppers into frosted cupcakes sprinkled with edible glitter.