I own a couple of adult sites that are pr3 and pr4 - do you think it could negatively affect my two mainstream (non adult) blogs if I linked from the adult sites to them -- of course not link back to them. what u think?
Linking to a site never affects the linked site negativily. Reverse it can do harm (bad neighbourhood). But in your case you only link from the adult sites to your blogs. So this doesnt affect your blogs negativily.
You won't get any negative effects as far as I am aware, not sure if the relevance of the sites you are linking from would lesen the benefits though? I'm sure someone on here could answer that. I'd like to know as I am in a similar situation.
If it makes sense to link to your main sites from your adult sites, go ahead. It will not harm your main sites. It probably won't help either unless it's a relevant and themed link (which I don't see how, but I guess it could).
It definatly won't do you any harm, it's when it is the other way round that it might cause problems.