Linking to big sites - relative PR

I've seen threads on this, where can I find them?

[NLightN]

There have been a few posts out there I've read on the subject of linking to high PR sites, even if they do not link back.

Can this help, if so, in what way?

Thanks

[MsRach]

I've not seen this. If it were so simple to improve your ranking just by linking to high PR sites, wouldn't everyone be doing it already?

[steveb]

[webmasterworld.com...]