Front wheel hub clicking?
 

I was out riding last night on some rougher terrain than I normal traverse, and towards the end of my ride I began to notice a clicking sound that I believe is located in the front hub. Went out again today and the clicking was more noticeable. The sound speeds up as I speed up, and slows down when I slow down.

Any ideas on what my problem might be?

Do you have a cycle computer? Check the magnet. Some of them make a little noise anyway, but there might be a rub.

No, no computer magnet.

Presta valve nut?

Sounds like a loose spoke. Try tensioning up on the spokes if you have the tools and the know-how. Sometimes the relative motion that is caused by a loose spoke causes fretting on the spoke seats or where the spokes cross, and in this case it is too late and the spoke(s) will have to be replaced.

You can try squeezing together nearly parallel pair of spokes with your hands and you will usually (but not always) be able to recreate the clicking noise.

Could be a bearing problem, too. I've had a rear wheel make a surprisingly loud clicking/rattling noise when the skewer wasn't very tight (ball drop when the bearings very slightly loose) and a front wheel make a soft clicking noise that went away when I replaced the pitted cones.

Does it happen on smooth ground?

Yes, it happens on smooth ground. I checked my spokes and a couple of them are pretty loose on the front wheel.

These stock wheels come out of true a tad too easy for my tastes. :notamused:

At rest close the front brake and see if you can make the clicking noise by rocking the bike for and aft or side to side.
A friend of mine had a loose headset that was causing a clicking sound.