Re-using text from a grant proposal in a paper (or vice versa)
Copying proposals to papers: I am sure many have not thought about this but many have copied material to and from proposals. Copying from a proposal to a paper should not be a problem since a proposal is normally not a publication and I have never come across a funding agency that claims copyright on proposal texts sent to them. If anyone knows of exceptions, it would be very interesting to know how they handle proposals. Taking the idea to the (silly) extreme one could argue that copying what you write in a notebook to a computer-written manuscript is self-plagiarism. The key lies in what sources are considered published and which are not. 

Copying papers to proposals: Copying from a journal paper to a proposal should normally not be a problem either since the proposal is not a publication and not something that should be distributed. But, the journal text may be subject to copyright so it makes sense to see to what extent one might infringe on those rights by copying text to  a proposal. I doubt any journal would care much (or indeed find out) as long as the proposals are not made public. Since most application processes are very strict and reviewers are not allowed to disclose materials (some actually ask you to physically destroy any printouts) I doubt there is a problem but strictly speaking this may indeed be a grey zone.

EDIT: I will add a definition for self-plagiarism: Copying material you have previously produced and passing it off as a new production from the site plagiarism.org. From this perspective the question becomes, is one trying to pass of the copied material as a new product?