Ask HN: How do you handle multiple (GTD) inboxes

I'm trying to get more organized at work and privately. GTD makes a lot of sense, but I'm struggling with the concept of just one inbox. There seems like there's so many different inboxes to keep track of - job mail, private mail, text messages, people dropping in to discuss, ideas popping into my head. How can I funnel all these things into one, central, inbox?