John Cage's experience in an anechoic chamber was instrumental to much of his thinking about music and silence. Or at least it made for a good anecdote that he used quite often:

"There is always something to see, something to hear. In fact, try as we may to make a silence, we cannot. For certain engineering purposes, it is desirable to have as silent a situation as possible. Such a room is called an anechoic chamber, its six walls made of special material, a room without echoes. I entered one at Harvard University several years ago and heard two sounds, one high and one low. When I described them to the engineer in charge, he informed me that the high one was my nervous system in operation, the low one my blood in circulation. Until I die there will be sounds. And they will continue following my death. One need not fear about the future of music."

I have no friends or family and I usually find Christmas less depressing.

The pride of my personal library is my copy of the 20 volume edition of the OED (2nd). I have it conveniently placed near my writing desk and make constant use of it. I fully appreciate the greater convenience of an online version but there's nothing quite like seeing it all laid out like this. While the market for something this expensive and large might be dwindling I doubt it will ever go away completely. And then at $295/year currently for the online version I just cannot justify spending that much (due to the weird price fluctuations at Amazon, and a lot of patience, that's the exact price I paid for my printed version). I also have the OED Historical Thesaurus which is an amazing work. The article mentions that they're going to combine it with the OED for the online version. That would make the yearly price more reasonable but it still seems more than I'd be willing to do for every year for the rest of my life.

I've given this a lot of thought over the years and I believe you can break it down into three circumstances

1) If you're using a monosaced typeface or a typewriter, use two spaces. It's the convention and I personally think it makes reading the text much easier. Of course how often does this situation arise these days? Not very.

2) With a typesetter or typesetting software a "space" has no specific length as it varies depending on the needs of the typesetter. That said some typesetters pad the space after a period and some don't. Either way it will look good and consistent. Trust your typesetter. Though if you use TeX you have your choice of which style to go with. It doesn't matter which you choose, it'll look fine.

3) If you're using a word processor it doesn't matter. Word processors produce crap for output. By using one you are stating up front that you don't care how the final product looks. By definition you are producing an informal text and as such you can use as many spaces as you want since it's not going to affect the aesthetic value or readability of the text any more than the decision to use a word processor in the first place. If you do care about how it looks and reads use typesetting software.