Check out these adorable office supplies, courtesy of the dollar bins at Michael's...
Trellis, zebra stripes, houndstooth and stylized mums. Nice!
I picked up some file folders and a couple notebooks, but there were also acrylic stamps that would make really cute paper weights, ribbon, giant paper clips, metal tins, blank notecards, notepads, magnetic weekly calendars for your fridge, etc.
I also picked up these napkins from the dollar bins. They're technically Christmas napkins, but I think they would be adorable any time of the year for a bright and cheerful birthday party a la Kate Spade.