You already know how to cut onions so they don't make your eyes tear, and it turns out there's something else you can do to avoid bawling while making dinner: refrigerate the onion for 30 minutes or chill it in ice water first. The latest issue of Popular Science (not online yet) explains that a volatile sulfur compound from the onion floats into your eyes to make them tear.
[The chill]slows down the action of [the onion's]trigger enzyme and saps some energy from the vegetable's volatile molecules.... It reduces the tendency for the sulfur compound to volatize.
Haven't had a chance to test out this technique yet, but if you do, let us know how it goes in the comments.