Steve Conway mentions on his site the large number of differing way Taekwondo is spelled, in particular "Teakwondo" comes up time and time again. I've always thought this must just be a simple miss spell on the part of the people using it, but have actually found an official source for this spelling.

Page 60 of the Taekwondo Textbook (the official guide to WTF Taekwondo published by the Kukkiwan) refers to Teakwondo. I found another version on page 78 - "Thekwondo" although I've never seen anyone using that particular one and hope I never will ;)