Freeware or Opensource electronic tools

[PeterD]

I'm looking for suggestions of good freeware or opensource
applications that are people's favorites...

Specifically I'm looking for:

1. Schematic drawing tools.
2. Circuit design tools.
3. Circuit board layout tools.
4. Circuit emulation tools.

My most important 'restriction' is that I'd prefer these tools to be
Windows based. I'd look at Linux or Mac tools but for the book I'm
working on I think I want to keep things just WIndows (let's face it,
Windows is the most common OS... <bg>)

Thanks!