This is a short guide on how to put LED's in the cupholders.
First of all, you have to remove the armrest assembly. It's simply held in place by 4 10mm bolts, one in each corner of the assembly. That is to say, there are two under the piece of felt in the front tray, ahead of the cupholders. The other two are in the console, under the felt bottom piece. Once you pull it out, you'l see they're pretty simple to access with a socket driver and an extension.
Make sure your e-brake is pulled up, and then lift up the back end of the armrest to expose the 12v connector. Unplug this and take the armrest assembly out of the car.
After this is done, you can take a drill to the middle of both cupholders. I had 5mm LED's with supplied mounting clips, so I drilled a 1/4'' hole first, and then widened it a bit by going up to the next sized bit. Test your LEDs' fitment on something unimportant first, your results may vary.
This is what it will look like. Note that I had one LED already in place, and had just drilled the second hole.
Both in place:
After your LEDs are in, secure them with some silicone on the inside of the cupholder. This will not only glue them into place, it will prevent water from getting into your wiring.
Then, you have a few options depending on how you want to wire them. I simply soldered both the positive leads together, adding a single length of wire on the end of the pair, to tap into the 12V power supply nearby. Repeat for the negative leads.
Now that your LEDs are in, secured, and wired together, you can put the whole thing back in your car. Use self-stripping tap connectors, or "Vampire clips" similar to these:
Remember that connector you unplugged when you took the armrest out? The white wire with the black stripe is the Ground, so tap your negative lead there. The blue wire with the white stripe is positive, so tap that for the positive lead. When you're done, tape up your new connections, and plug the connector onto the 12V outlet.
Your newly-installed LEDs should light up when you turn your key to the On position, as they're wired to the car's 12V system.
Pictures of the finished product:
They're very bright and light up water / gatorade bottles really well, but they're not blinding. It was well worth the effort to get these in!