One of my Twitter friends wished that you could use Quicksilver to append to an OmniOutliner document. This took me 5 minutes to whip up. I got the entire code from MacScripter and then wrapped it up as a Quicksilver action.
It’s pretty simple to use. Save it in your Quicksilver actions folder, restart Quicksilver, and give it a go. It lists the topics of your frontmost OmniOutliner outline and appends the text to your topic of choice.