On UNIX and UNIX-alikes, such as Mac OS X and Linux, you can use the readline module. On Windows you can use pyreadline.
If you do it the way minitech suggests in his comment, write a little function to make it easier:
def input_default(prompt, default):
return raw_input("%s [%s] " % (prompt, default)) or default
name = input_default("What is your name?", "Not Sure")