Grammar Point of the Week： 擬態語・擬音語 Otomatopoeia
This isn't really an entry of a specific word, but I found this Japanese Google dictionary for onomatopoeia. According to its little blurb, onomatopoeia is often used in emails, blogs, etc, and can be used to create an atmosphere of affinity (?) for your reader. I think it would be a good way to "piddle away some time", instead of checking facebook or your email for a moment. You can browse the terms by their first syllable, and learn the various onomatopoeia that can be associated with a certain verb. These terms are used quite a bit, so they are a useful thing to learn. Some you can guess just by the quality of their sound; for example ザーザー降る is used when it rains heavily and violently, and you can probably understand that by the voicing of the ザーザー and the way the a is drawn out. It just kind of gives you that feeling, doesn't it? But you shouldn't rely on guesses for everything, so check it out!