Using IContentFinder to get content outside of the main content tree in Umbraco 6.1 to replicate the behavior of the pipeline in v4 that allowed you to view content outside the main content tree by its assigned URL. Based on the Gist by Lee K.

IContentFinder example

using Umbraco.Core;
using Umbraco.Web.Routing;

namespace Website.ContentHelper
{
	public class ContentFinder : ApplicationEventHandler
	{
		protected override void ApplicationStarting(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
		{
			ContentFinderResolver.Current.InsertTypeBefore<ContentFinderByNotFoundHandlers, ContentFinderCommonPages>();
			base.ApplicationStarting(umbracoApplication, applicationContext);
		}
	}

	public class ContentFinderCommonPages : IContentFinder
	{
		public bool TryFindContent(PublishedContentRequest contentRequest)
		{
			if (contentRequest != null)
			{
				var path = contentRequest.Uri.GetAbsolutePathDecoded();
				var node = contentRequest.RoutingContext.UmbracoContext.ContentCache.GetByRoute(path);


				contentRequest.PublishedContent = node;

			}

			return contentRequest.PublishedContent != null;
		}
	}
}