I have my own script that does it when it generates the html files...
I found this just by googling around, but have never used it so I dont know how well it works:
http://www.freedownloadscenter.com/W..._Compress.html
One thing to note is to keep two files, one with and one without whitespaces. If you ever want to update the page it is nearly impossible to do if there are no white spaces...
So it adds extra work, and like I said, I don't know how much it helps.
From the link above:
"Compression of HTML allows it to download faster, display faster ( the parser does not have as much junk to deal with), take less space on web servers and end users system, decrease loads on a server."
But they are trying to get ppl to use their product. If it does nothing else I do know from personal experience that it significantly reduces file size.