"Most modern kayakers associate a single blade paddle with canoes. However, single blade paddles have been used for centuries in kayaks, especially in the western arctic, Alaska and Siberia. Koryak, Chukchi, Aleut, Kodiak, Bering Sea, Bering Strait and Mackenzie Delta hunters used single blade paddles. Kodiak and Chugach paddlers used single blade paddles almost exclusively."
Tuktu Paddles has a great page on single bladed paddles. I especially liked the King Island designs. These plans for these same paddles is available in PDF form from David Zimmerly's page on Artic Kayak paddles. The 1st design with its recurved blade is interesting to me. I've already cut out two blanks with the this design - a one-piece birch and a walnut/cherry/laminated combo.
King Island Single-bladed Paddles UM #8565 & #8566
Hidenao Matsubara of Indian Canoe Craft has a photo of a single blade paddle with his baidarka. See below
Matsubara's beautiful carved Baidarka paddle
Finally, Harvey Golden's amazing pages on Traditional Kayaks contain some images of single blade kayak paddles
Eskimo Seal Hunter--Bering Sea.
Kodiak Three-Hole Baidarka
Yuit Kayak, likely taken at Nome.