Multiple domain names with 301 redirects

Need advice...

I have a few domain names that I have redirected to sections of my forum. And am not sure if this is the best method for SEO.

The homepage and main site is www.ecoforumz.com

On the home page I have different forums. What I did was redirect different domains to the specific forum.

For example...

On the homepage I have the below forums and have a domain name that points directly to the forum.

Green forums - has www.greenforumz.com pointing to it
organic forums - has www.organicforumz.com pointing to it
global warming forums - has www.globalwarmingforumz.com pointing to it.

Is it better just to point all domain names to the same homepage?
Should I submit each of these domains to search engines?
Should I not use 301 redirects and use the .htaccess file instead?

Any and all advice would be much appreciated.

I thought I had submitted a reply to this thread already. Strange. Maybe I did not complete the post.

I recommend that you use one domain only. Promote only 1 domain with the search engines.