WARNING: This post was originally published in 2008 and hasn't been updated since.
The tips, techniques and technology explained here may be outdated. If you spot any errors, please let me know in the comments so I can adjust the article. Thanks!
The following 2 pictures show a clear difference in system calls between a Linux' Apache, and a Windows' IIS. Draw your own conclusions. :-)
First up: Apache.
Followed by: IIS
They both seem chaotic, but the Apache one shows a lot more structure than the IIS one, which seems to be tangled up in its own web.