My jack russell terrier had one of these on his belly a couple summers ago.  I noticed him scratching a sore on his belly, he was pretty miserable for several days.  I watched it very closely every day, even put a little ointment on it until one day I noticed it was open.  I was holding my dog upside down and it poked its disgusting head out and WIGGLED.  I ran to the sink and pinched it, and it POPPED OUT like a gigantic zit.  I sent it to its disgusting demise down the disposal.

I saw an even bigger one come out of a rabbit at a vet's office.  DISGUSTING, and yet, completely fascinating.

From Wikipedia: "Removal processes include placing raw meat on to the area, which in theory will coax the larva out. ... Additionally, one can attempt to seal the breathing hole of the larva with nail polish, vaseline or adhesive tape and then, after a day, squeeze out the suffocated, dead larva."
~~ faints ~~

i am SO not watching that video. 

i prefer my grotesqueries to be imaginary.

@ girlfromnorthcountry.  Where did this happen?  We don't have them up here do we?  I thought they were in places like Central America.  I saw some show on Animal Planet about a guy who got one in Costa Rica.  He put vaseline and plastic over the whole and waited for it to come out.  It came out partway and them he pulled the rest out with a pliers.  It was one of the most disturbing things I've ever seen.

If you like bot fly, you're gonna love the latest Radio Lab:  http://www.wnyc.org/shows/radiolab/episodes/2009/09/25

(and I second sjixxxy's recommended listening)