With reference to Hart’s rules i’d suggest to put web addresses like this [www.webaddress.com]. Or without brackets if you set it that way: http://webaddress.com, no colouring or underlining.

You can see it here that if you set it in brackets without the http:// there is no colouring through the word processor.

We substitute angle brackets (U+2329 and U+232A) for the usual "less" and "greater" characters. This for university press book work, no complaints yet. Kerning is needed, both with the angle brackets and the slashes (esp. the two slashes). Of course, most fonts don't have these characters, just one more reason to have a EULA that lets the end user modify the font.

As for breaking, don't hyphenate (i.e., add a hyphen), and if you break at a period, the period should come down.

> but if it is too long to fit on one line in a column...

I hate putting long URLs in print documents, as they look disruptive and it's difficult for a reader to actually copy and use that URL. So in cases like that, I usually ask the writer if we could try a different approach, such as just using the site's home page URL, or putting the long URL in a footnote, or some other workaround. Sometimes they agree to a change like that, sometimes not.

An alternative is to provide directions, e.g.

[typophile.com » forums » design]

We have to put ’em in journal body copy all the time. No special styling, no brackets. Break after slashes, underscores, question marks etc (but, as Charles says, before a dot or it'll give the impression that the sentence is finished). Suppress hyphenation, and if the actual URL already has a hyphen in it, then try not to break at that (or it'll look like you've hyphenated) – take the hyphen over to the next line if you must break there. If there are no suitable punctuation marks to break at, but the URL contains strung-together-words (like www. thisisasamplewebaddress.com) then split between words (still without inserting a hyphen). Readers should be savvy enough by now to know that URLs don't have word spaces in them. If the surrounding text can be massaged to keep the URL on one line, all the better. Check long URLs that have got a lot of query gubbins on the end of them – you can often trim a lot of that out and still link successfully to the intended page.

I just checked my Associated Press Stylebook. It recommends using the http:// at the start, and a period at the end if the URL ends a sentence. And, if an address must be carried on multiple lines, "split it directly after a slash or a dot that is part of the address, without an inserted hyphen."

AP also advises to use URLs in running text only when the story specifically mentions a website. If the address is being used merely to direct the reader to a source for additional information, the Stylebook advises putting it in a note at the end of the story.

When an address is followed by a punctuation, I like to add a space before the punctuation to make clear that it's not part of the address. This is especially useful in e-mail and any other online medium where the address might be automatically converted into a link by software. It also makes it easier for the reader to highlight and copy it if they're saddled with "smart" highlighting. But I think it has a place in print media too. If it ends in ".com" you probably don't need the space, but if there is a full path, it's good to assume that some of the readers you're asking to retype the whole address are going to need all the help they can get to do it right.

http:// is important, because some pages don’t have www at the start.