Any suggestions for removing the smell of dog urine from carpet?

Sure - I'm not sure how this works theoretically, but it worked for me
in practice:
First saturate the carpet with plenty of baking soda (work it into the
carpet pretty well), let sit for a few days.
Vaccuum thoroughly.
Second, make a vinegar solution (maybe 10% vinegar?) in a wet carpet
cleaner/steamer, go over the spot several times with that, then vaccuum
as much as possible to dry.
(Baking soda alone didn't fix the problem, but I didn't try any enzyme
treatments or specific pet cleaners)
No more pet urine smell from my carpet,
Andy