I have most of the products for Descent 2 but don't get to play often. At this time, my wife and I like to play single quests instead of a whole campaign. There are so many quests to choose from - I'd appreciate some recommendations of quests that would be great for us to play as one-offs.

There are several quests in the the quest vault designed to be one-offs. In terms of official material, I'd shy away from introductions and finales, as these tend to be either overly straightforward (designed for low level heroes) or dependent upon the campaign that has preceded. I also generally avoid Labyrinth of Ruin for this purpose, unless you want to randomly assign skills to the ally (otherwise they may be underleveled if it is an earlier quest.)

Almost any other quest can be played in epic style. For the most part, I have found both "The Shadow Rune" and "Shadow of Nerekhall" to be great sources for one-off maps in terms of the large campaign books, and almost any quest from a mini campaign is enjoyable on its own.