I agree with Ryan on many aspects of SEO. In this situation, we diverge to a certain extent.
For me, it's the concept of 301 Redirecting any content you have on a site at all. If you have the content, it should be indexed. It's really that simple. Because by redirecting it, you're telling the search engines it doesn't exist. Which is not true.
So you're doing the redirect not because a page has actually moved, but for pure SEO reasons. And that is, in my opinion, a direct conflict of SEO best practices tenets that you consider your users first and foremost, NOT the search engines.
In this view, if you're doing a 301, it's because there's something else improperly occurring regarding your SEO methods. You're treating the symptoms, not the cause.
Treating symptoms and not the cause may work today, however over the evolution of SEO, it has always proven to be a myopic view and ends up not providing the long term value that only treating the cause can do.
So either actually delete the content you don't want, or move it - you can even make it a permanent page within the area of the main site - as a sub-link from the highest level page you want ranked. Then you can do a 301 redirect, which is valid use of the redirect function.
Or leave it as is, and focus on building stronger content and signals to the pages you prefer to be ranked.
The only pages that exist on a site that should not be indexed are pages that include member area sign-in pages, secure shopping process pages, and similar pages. And those shouldn't be 301 redirected - they should get the noindex, follow treatment if you want their on-page links to main site pages adding to the site-wide overall strength, or they should be noindexed in the robots.txt file altogether.