I use Speedo Contoured Paddles ($14.95 at Sport's Authority). I think mine are medium. They only go about 1 inch past my finger-tips. I've always heard that using bigger paddles can cause shoulder injuries.
They are the red/size medium - much bigger than what most people in my Masters group are using, but the description said they were for triathletes. I've been using them for over a year now but have only thought twice about it since joining the Masters group and everyone is WAY faster than I am when we use the paddles. I'm wondering if they are too big/slowing me down?