This recipe is still a work in progress. I made it up on the fly, and it turned out really well, but I think I'm still tweaking it.
3 or 4 onions, thickly sliced
About ½ C brown sugar
About 1 T each pepper and salt
About ¾ T each onion powder, garlic powder, chili powder, mustard powder and ginger
Approximately 3½ lb pork Boston butt (aka pork shoulder or shoulder roast)
Juice of 1 lime
Lay the onions in the bottom of your crockpot. Combine sugar and seasonings and rub over meat. Put meat on top of onions, pour the rest of the rub on top, cover and cook on low for 10 hours. When done, shred with two forks. Mix in the lime juice. Serve on buns.