After reading about and trying various time- and energy-based contexts that other people have proposed, I've settled on breaking my Desk list (@computer) into Desk, Email and Web. Almost all of my quick or low-energy next actions involve either email or the web, and I don't have to think hard about where things go. (Let's see, a next action requiring medium energy and 23 minutes. Hm. Oh, that goes on the "Hm" list) If I want to, I can do web and email from an iThing too.