Prodrome

Meaning: forerunner or precursor; or introductory treatise or book; or symptoms characteristic of the onset of a disease.

Usefulness: 1 (I think this should be adopted as the name for the commercial preparation for Christmas, the secular equivalent to Advent. "Thank goodness the prodrome is nearly over; after two months of relentless tinsel-covered mercantilism, I'm not sure I'll have any festive cheer remaining for the feast itself.")

Logofascination: 1 (Another running word, part of the dromos family mentioned previously in hippodramatic and dromomania.)

Tumbleweeds

Meaning: Besides the literal meaning, it is used to mark or describe an awkward pause in a conversation, generally because one of the participants has said something particularly foolish or embarrassing. For example: "I made a joke about eating frogs, but it turned out she was French, so, tumbleweeds..."  Also heard/seen as tumbleweed (singular), or tumbleweed moment.

Usefulness: 1 (Even if people haven't heard this before, they will generally grasp what you mean - it's a clear visual image.)

Logofascination: 1 (The logofascination lies in this sense of the word evolving before our eyes; I first saw it on the internet several years ago, but the Virtual Linguist hadn't heard of it in May 2011. Although it's been a visual symbol for some time - see video below - it has flowered into a symbolic term and conversational marker in the last ten years* or so. One never knows with words, but I suspect this symbolism will last, as the visual symbol has.)