I have a couple domains available to me that are related to my industry. They are old and have a little PR. Is it worthwhile to buy these domains and do a permanent redirect to my domain purely for the SEO benefit? I guess the real question is, is there significant SEO benefit from redirecting old but relevant PR domains to another site?
What kind of PR do they have? PR 2? I would if it has a PR 3 or higher. But I might redirect one, and use the other one as a resource. Make it a micro site/blog and keep it going. Pass links to your site whenever you want and you can sell ad space and make money off it. That is if you know how to keep the PR from a previous Domain.
I would use the two domains to link to your main domain using in-content links (not redirecting). It will be better if you put the two domains on different IP addresses.