I've seen huge butchers blocks that essentially is a table with a butcher block top. How do you clean such a thing if you can't wash it in the sink? Should those blocks only be used for vegetables and not meat because it can get messy and hard to clean (oil and 'juices')?
You can certainly cut meat on these, I have a large end-grain cutting board that is too large to wash conveniently in my sink.
There are a number of methods to clean them:
Soap and Water
Soap and hot water are best for regular cleaning. Just get a rag or brush and scrub it. Dish soap is just fine for this use. Make sure to rinse and dry it thoroughly.
If you don't mind the smell you can use undiluted white vinegar to clean and sanitize your surface. If you keep some in a spray bottle you can just spray it down and wipe it with a paper towel. If you have a big oily mess, I'd suggest starting with the soap & water method, and finishing up with vinegar.
Vinegar is apparently very effective at killing microbes, surprisingly more effective than harsher quaternary ammonium solutions.
A little goes a long way with this. You only need a teaspoon or two for a quart of water. Just spray it down thoroughly, let stand 5 minutes. Finish with rinsing and drying. Like vinegar this is best as a followup to soap & water for a really messy board.
If you have strong garlic, onion, fish, or other smells in your butcher block you can cut a lemon in half and rub the board down with the halves. Lemon juice is a weak antiseptic, so this should be used primarily for odor control and not as a sanitization substitute.
Note that regular cleaning also requires regular seasoning of your block surface. You should oil your board/block once a week, or more with frequent use.
Professionally you scatter the surface with sawdust and then 'scrub' the surface (dry) with a metal brush. This takes off the top surface and removes any blood, etc, which is why if you see an old butchers block or one that has been in good use it will be worn down considerably. In a domestic setting I suppose that would be more difficult (but by no means impossible). Vinigar is an excellent cleaner, as Hobodave and Yossarian said, but I wouldn't use bleach on a butchers block, or wood in general really. Better for plastic chopping boards if you are going to use it.