Last night, about half way through my ride I heard/felt a faint pop in the crank of my Specialized Allez. There was no discernable difference in the bike's performance, i.e. no increased pedal resistance. In fact, my average MPH was the highest it's been since I started riding again. However, what I did notice is an annoying clicking sound coming from the crank while pedaling. I figured that maybe it just needed a good lubing, being as I hadn't applied any for the last 300 miles or so. So before tonight's ride, I very generously applied lube to all moving parts, and despite a very graceful ride, the clicking persisted.

The bike is 4 years old and nothing has been replace with the exception of adding spd pedals. I'm just curious what the community here might think the culprit is. My gut is telling the bearings in the bottom bracket need servicing, but what do I know? I'll be taking it in to the bike shop on Wednesday.

Bearings in the pedals. Sometimes the bearings are not greased properly on new pedals.

So ruling out anything that you could miss such as the pedal hitting an air pump or your shoe hitting the crank arm on each stroke, could be related to the BB or the crank gear -

Does it do it on both front chainrings, not just big, not just small, etc?
Does it do it once per crank rotation, always, no matter what?
Or does it do it once per chain rotation, etc?
Any chance you can take a video of it doing it?

My road bike developed a nasty pop/Crack like sound coming from what I thought were the bearings, always at the high point of the right side crank.
After regreasing BB bearings and pedals, noise was still there.
Removed the chainrings, cleaned and lubed the 5 nuts and bolts, noise gone.
Knowing that, I would get the simpler stuff first out of the way.

Sounds like a broken chainring bolt possibly.

I assume the clicking sound is rhythmic, it occurs at exactly the same point with every rotation of the crank?

The first time that happened to me, it turned out to be the cleats on my SPD-SL shoes/pedals. To me, it clearly sounded like the clicking was coming from the pedals (and they weren't that old so I was wondering if they had already worn out) so I called the Shimano tech support line and they told me to do this: put a little grease on the "tongue" on the front of the cleat and the flat part at the back of the cleat - where they engage with the pedal. The noise went away.

This may, or may not, work for you but it's a freebie worth trying!

this was my first thought

Drivetrain noises can be the oddest thing. Sometimes as simple as the ends of long shoe laces striking part of the bike.

Some good tips that I will be trying on my Specialized Roubaix. The right side pedal area makes a rhythmic noise with the pedal around the 3:00 position

Lube your seatpost and the collar. It's worth a try.

Pedal bearings? Bottom bracket?

Maybe the clicking is a part that isn't supposed to move but is. Tighten the cassette, crank arms and chainring bolts? Cleats?

Get up on the bike while leaning against a wall or holding onto a railing. With wheels stationary & nothing rotating put hard downward force on the pedals. If you hear the clicking or creaking then it's most likely a busted/loose chain ring bolt.