Some of you will recognize this post from the Indiana thread. Read it again, it has vitamins.
Okay, here's the deal. There is nearly unanimous agreement that putting some wood ash in your dust bath is good for chickens. (Er, in your chickens' bath, that is, not yours. Ash in your own bath will make you... well, ashy. And it won't help your chickens unless they're in the bath with you.... and I'm not going any farther with that train of thought. There are kids in the room.) Benefits of ashes for chickens may include preventing parasites, external and/or internal, keeping chickens ironically clean (ashes are dirty) and who doesn't love an ironic chicken? Also it will probably give your chickens super powers like Flying Tornado Kick that can dismember coyotes, and the patience and wisdom to negotiate peace in the Middle East. At the very least they'll be able to change the oil in your car, which is dead useful if not as impressive.
So, where do you get wood ash? As far as I can tell, you can't buy it on the internet. Except maybe if you did a "wanted" ad on craigslist, but I wouldn't do that because then there's no telling what's in the ash. Could be all sorts of toxic chemicals or burned up bodies because some people on craigslist are serial killers. Everyone knows that. Anyway, as shocking as it is, I finally found something that cannot be purchased online. Go ahead and prove me wrong. I double dog dare you. (someone on the IN thread did, but he cheated

)
However, the overwhelming majority of us can make our own. All you need is a place where you can burn stuff, and it doesn't have to be a big place. And old grill or bbq cooker will do. If you find yourself in the unenviable position of living in an apartment where even small patio grills are not allowed, then I weep for you, but you're going to have to just find someone who is willing to do this for you. Oh look, here I am! PM me and we'll work it out. Not kidding.
So get out your grill.** It's been pointed out that the ashes that are already in your grill are probably greasy, so don't use them. There is also a chance that you've been using "charcoal" briquettes in your grill. If you have, I am going to resist the temptation to judge you. Shameful as it is, I once did this too... most of us have been in that dark place at least once in our lives. Today is a new day, and you're going to step out into the breathtaking light of a whole new world! A world where delicious, smokey meats can be cooked to mouth-watering perfection in the convenience of your own yard without the bitter aftertaste of noxious petrochemicals. It's a glorious life, and a joyful life, and you'll never look back. More to the point, you can't let your chickens into briquette ash because it's poisonous and will probably cause them to writhe in agony and die. No one wants writhing chickens.
So go buy some lump hardwood charcoal for your grill. Then go buy some meat, because to make a fire without cooking meat on it will disgrace you in the eyes of your primeval ancestors. Okay fine, you can grill some veggies if you don't eat meat. After all, everyone is entitled to their wrong opinion. But for heaven's sake cook something with your fire!
Now the trick to this is not to get any of the meat or it's drippings on the ashes, and there are several ways you can do this. They all involve indirect heat; how to do it depends on your grill. If you already have a bbq cooker with the fire box on the side, then you're good to go. Just dump any immoral briquette ashes, if you have any, and fire it up with lump charcoal. Done deal. If, like me, you merely covet a bbq cooker from afar, you can still use a regular weber-style grill. The bigger the grill, the easier this will be, and the more ashes you can collect. Once again, start by dumping all of your previous ashes, and give a quick wipe to the inside.
Now, most American grillers are accustomed to direct heat grilling. The meat goes directly over the burning coals and viola, you have not-raw meat. You also have grease-contaminated ashes, and no one likes greasy chickens. So instead, you want to use indirect heat. The charcoal goes on one half of the grill, and the meat goes on the other half. There are many benefits. Your meat will cook longer at a slower temperature. For burgers, this means a more tender burger. You'll be surprised by the difference it will make in brats. And if you've never attempted real bbq on your little webber, this is how it's done. A word of caution, though - if you're going to bbq chicken on a lower, slower heat, you'll need to protect it from drying out by brining it first, for at least two hours for a whole bird, or one hour for thigh and breast pieces. I do mine whole and butterflied, and I soak them overnight. The results can be spectacular. If you have no idea what brining is, google it or PM me.
You'll want to put some kind of collection pan under the charcoal side to catch the ashes, and it will need to be sturdier than aluminum foil, because the ash will be hot enough to burn through. A cheap, but not disposable, pie tin ought to do nicely. If you're slow-cooking whole brined chicken, and you should be, you'll also want a pan under the chicken. What runs out of the chicken is stock, and if you brine a whole bird overnight, the stock that comes out should be diluted by half and will be better than anything you can buy in a can. I do this in my crock pot all the time; it's the best, easiest, cheapest stock you can get your hands on. PM me for details if the process is unclear to you.
If you have a tiny apartment grill, indirect heating can be problematic, but it's still possible in small batches. Another method you could use is to stuff your chimney starter full of charcoal, set it in the bottom of your little grill (all wire racks removed) and fire it up. Roast hot dogs and marshmallows over the chimney starter, so you get some use of the heat. The grease off a hot dog should be negligible, and it will mostly burn away in the fire anyhow. Collect the ash after it burns all the way down and cools off. If you don't have a chimney starter, get one. They're cheap, and almost the only way to start lump charcoal burning.
That's about it! I'm going to do this myself at the very next opportunity, and I'll let you know if I run into any other snags. Happy grilling and ashing to you all!
** If you only own a propane grill, go back inside and cook your meat on the stove, because it's exactly the same thing. I have nothing further to say to you. Infidel.