Many Domains: One Site (Redirects)

Any search engine penalty?

[HHEAdmin]

I have a main site and short keyword domain name which I use as the host domain (say blue-widgets.com).

I also have blue-widget.com. For some reason (well, I know why - because a PR5 link page links to it though the descriptive text they have for it is slightly inaccurate), blue-widget.com is PR3 while blue-widgets.com is PR0. Only the homepage has any PR.

I have also bought several other domains, mainly longer keyword ones (e.g. blue-widget-trading.com, buy-blue-widgets.com).

I have two questions on how best to use this setup:
1) Should I take advantage of the fact that blue-widget.com is PR3, and focus my link campaign on that rather than its plural? However, I think the plural is a likelier search term for the service I provide.

2) Should I link up the other domains (point them at blue-widgets.com), or might there be repercussions from the SEs from doing this? I bought them partly because if I didn't someone else probably would, and partly because of their keyword value.

[specter]

No,you willn't have any repercussion by redirecting other domains on the main one,just no benefits from that.
If I was you I would keep my PR3 domain and I'd concentrate my efforts on its SEO,meaning that for SEs no matter singular or plural of a considered keyword (Google in particular,simply ignores the ending making a partial matching).