If you use Safari you can use the standard clipping shortcut (you can set it in preferences). You need to select some text on the webpage and then hit your shortcut key.
If you use Gmail/Google Apps and are in Firefox or on a Windows PC away from your computer (at work, say), you could try and see if my bookmarklet works for you:
http://paulstonedesign.com/blog/arti...-to-omnifocus/