If you're looking for better light using your on-camera flash, Photek's Softlighter Hot Shoe Diffuser Kit (46") fits the bill: you get a 46" umbrella with a white interior and black removable cover, a diffuser panel with an opening for a hot shoe flash (not included) and the umbrella shaft, a set of Velcro tabs for the flash head, a hot shoe umbrella/light stand adapter with an adjustable hot shoe locking plate for mounting the flash/umbrella to a stand, and a set of silver and gold discs for modifying the color of the light. This setup gives you a broad, soft studio-quality light using only a battery-powered "on-camera" flash.
Softlighter Hot Shoe Diffuser Kit (46")
OP Series Umbrella (White Interior & Removable Black Cover)
Diffuser Panel With Velcro Opening for Hot Shoe Flash and Umbrella Shaft
Set of Silver/Gold Light Discs
Set of VelcroTabs to be Attached to the Hot Shoe Flash Head