How can I get the crankshaft bolt undone so I can change my timing belt?
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This question shows up in the newsgroup quite regularly. The bolt holding the pulley to the crankshaft is on there TIGHT. Some folks have had so much trouble getting it started they've posted plaintive enquiries wondering if it's a left-hand threaded bolt! No, it unscrews the regular way, but don't kid yourself that you're going to undo it with a short-handled wrench. Having the car up on jackstands probably won't give enough room to swing the handle of the wrench you're going to need.

Also most Honda engines have a special quirk that very few engines do: They turn counter-clockwise, backwards from the industry norm. With any other manufacturer, you can wedge a wrench up against the frame just so, then blip the starter to crack the bolt loose, which happens to be a very effective and non-destructive method. Not so with Honda, which is why we have such problems. The only two exceptions to this rule (that I'm aware of) are the Acura 1.7 EL's engine, and the 2.7L C27 as installed in some Legends. They are Honda's only engines that turn clockwise when viewed from the front, and whose bolts can be loosened with the wrench-on-the-frame trick.

The physically easiest way to get the bolt loose:

An impact wrench. The best method by far.

DeWalt 250lb electric impact wrenches are available from any industrial rental place for less than $20 per day. You might have to buzz back-and-forth (tighten for a bit, loosen for a bit, etc.) for a minute or so, but it will probably eventually come free. Mine did, and I live in the Rust Belt. These are very handy as they require no $1,000 compressor.

If the bolt does not let go no matter how long you buzz with the DeWalt, you'll need some heavier artillery: An air impact wrench backed up by a big compressor. If a regular 1/2" drive air wrench won't work, try the Big Bertha of impact wrenches: A 3/4" drive 600 ft-lb job.  If even Big Bertha fails, or you can't get your hands on a gun that big, a blow or two on the crankshaft bolt with an air hammer (rentable) will break the seal that's locking things up. Don't worry, you won't damage anything by whacking it with the air hammer. Garages do this on a daily basis. You can even try a hard whack with a regular 16oz claw hammer, but don't miss, or you'll bend something expensive!!!!

If you don't have an air wrench or compressor, you can go to a nearby garage and ask them to buzz the bolt loose for you, then snug it up again, just enough for you to get home. Might cost you five or ten bucks or so, and the mechanic/garage may not even charge you if they don't have to put the car on the hoist. Worth a try, anyway.

The beauty of any impact gun -- air or electric -- is that because of how it works, the crankshaft and the engine itself WILL NOT MOVE or rotate at all as you attack the bolt. This means that your careful TDC setting won't be disturbed, and you don't need to worry about trying to keep the crank from turning while you work.

Manual methods: Not as desirable, but if you have no access to the electric impact wrench or air tools, the only way

One possible serious problem with any manual approach to removing the crank bolt is tearing of the upper engine mounts. Since you'll be applying a large amount of force over a large amount of time, you will end up pulling the engine in the direction of your efforts. Pull it enough and you run the risk of over-stressing the upper mounts. In the vast majority of cases, just pulling with all your might is utterly futile. I'd try an impact gun, or the pulley-holding tools mentioned below before simply hauling on it with a breaker bar.

With manual tools, a new problem arises: How to stop the engine from turning when you apply the necessary torque with a half-inch drive tommybar whose handle has been extended with a length of pipe. Just having the car in gear won't cut it. Jamming a big screwdriver into the teeth on the flywheel works sometimes, but it's a good way to risk tearing up the ring gear.

Luckily for us, Honda has already thought about this. Honda has used a number of pulley designs over the years, and  they have included features on the pulleys that are designed to receive pulley holding tools. These tools are available commercially, or are easily constructable by you.

For Hondas with a hex aperture in the pulley, the proper way is to use the tool pictured at the front of the shop manual. It's essentially a length of hexagonal pipe with a handle welded to it. It will fit into the hex hole in the pulley and allow a deep socket of the proper size to pass though and get hold of the bolt.
Two posters, "jamieson" and "Curly" combine here to offer this home-made version of the Honda "special tool".

A professionally-made tool is available here, and below...

Canadian Tire in Canada (and surely other places as well) are now selling an inexpensive version of the hex tool. A contributor snuck this hasty picture at Canadian Tire. If he wasn't so worried about getting kicked out on suspicion of industrial espionage, the pic might have been better...