Two Spaces?

I saw this discusion over at another board, and it got me thinking:

Do you to two spaces after a period or one? My Mom has always told me to do two spaces, but in other classes it was only one.

I know that some people do it just because they were brought up that way, but my question to you guys is, do you do two spaces after a period or one? What were you brought up learning?

Just looking for an interesting disscussion on this :smiley: