Hi Craig,
Depends how much you want to spend...
A tight budget made me look around carefully for eyepieces for the moon and planets.
Finished up buying 2 University Abbe Orthoscopics, 12.5mm and 5mm.
Very happy with them, nice sharp views, and the price was brilliant, although I notice they've gone up a bit since!
Check them out at:
http://www.universityoptics.com/125inch.html
My research on IIS and CloudyNights suggested these were a good choice, and the recommendation was that it's better to buy individual eyepieces rather than use barlows.
Cheers
Chris