There is NO consensus, as in a previous thread:
http://typophile.com/node/27727

In the US, Chicago Manual of Style says no spaces around dashes but sometimes you need to kern or add a thin space when they are too close to the type. The UK seems to have a different style.

I found another thread on this subject too...
http://typophile.com/node/27727

I should add that I'm a traditionalist on this score - but I come from book publishing where the editors are real sticklers for Chicago. It is most important (in my book pardon the pun) to be consistent in your use of dashes so as not to confuse the reader. The em and en dashes should be distinct from one another both in style and usage. Unfortunately their length varies widely from font to font.

Depends what dashes you use, in what context, and also where/in what language: Apparently, there's a "tradition" – or at least a tendency – in anglo-american countries to use them without spaces, but with spaces in contentinal europe. Having spaces around dashes appears to become more and more popular in anglo-american countries, too, as of late. I think there's a thread on here where your topic was discussed in full length…

As you can already see, pattyfab is right, there is NO consensus…
Note to self: mujst refresh before posting.

I think the consensus was "pick one way of doing it, and be consistent within your document." ;-)

Which is always a good rule to work by....

AP style is to "put a space on both sides of a dash in all uses except the start of a paragraph [their version of a bulleted list] and sports agate summaries." See "Punctuation" chapter.

Chicago style is not as explicit, but all the examples in the 15th ed. do not contain preceding or following spaces (e.g.: "It was a revival of the most potent image in modern democracy—the revolutionary idea."). See sec. 6.87ff.

Strunk & White are not explicit either, but also do not include spaces (e.g.: "The rear axle began to make a noise—a grinding, chattering, teeth-gritting rasp."). See sec. I.8.

Bringhurst recommends using en dashes set off with spaces: "Used as a phrase marker – thus – the en dash is set with a normal word space either side." See sec. 5.2ff.

I don't have MLA or APA style guides handy, but I'll hunt around for 'em — er, (bad) pun intended.

Sorry. Double post.

The style I like to follow is to used a space around the en dash when it is used in place of an em dash (which often breaks up the color of a page). However, where an en dash is expected (war of 1914-18, pp. 33-45, etc.) then there should not be any spaces.