tedster - 3:59 am on Sep 28, 2012 (gmt 0)
It certainly is OK. I do it a lot for brand name protection, typo handling and the like.
keyword.com - canonical domain
keywords.com - 301
keywords.org - 301
keword.com - 301
It's also a good way to handle a business acquisition. I know of one business who owns 1300 domain names that all redirect to their core name.
Just one word of caution - only do marketing for the canonical domain name. That is, don't try to promote the ones that redirect.