Spoke Problem: A little help?

[The Borg]

Ok...so, I swap out a new front tire this weekend, and decide to give my bike a bath (just got caught in a ripping rain storm a few day prior).

So, I'm cleaning my rear wheel, and notice that it's not spinning true...it's kind of wobbling as I rotate it.

I notice that a spoke has broken away down near the hub. This is at the same place that up near my brakes that the wheel is 'wobbling'.

How serious of a problem is this? How in the world do I repair a broken spoke? As I look at this, I don't know how I would get another one in down by the hub.

If any of you have a little insight, I would appreciate it.

Thanks in advance