I was all ready to say "Spark plug O-rings" when I noticed you said *front* left tire.
The brake/clutch master cylinder sits right in that area, although it is closer to the back of the tire. If there is a small leak at the bottom of the reservoir where it sits into the top of the cylinder with an o-ring seal then possibly some fluid could drip out, and maybe get on the tire and get moved to the front of the wheel well liner and drip down. Another possibility might be the brake caliper or bleed screw weeping some brake fluid which would drip down onto the wheel and get spun forward.
There is not really that much else up there, there are some radiator tubes that go near there but I wouldn't think it would be caramel colored/oil like. What does it feel/smell like? If you open the coolant cap in the rear trunk does it look like that fluid there? Does it match the fluid in the master cylinder?
Master cylinder:
http://www.pelicanparts.com/techarticles/Boxster_Tech/48-BRAKES-Bleeding_Brakes/48-BRAKES-Bleeding_Brakes.htm
Coolant:
http://www.pelicanparts.com/techarticles/Boxster_Tech/29-WATER-Flush/29-WATER-Flush.htm
Power steering? I don't think it routes that close to the front of the car.
Steve