One of the keys to packing light is to remember that clothing can be washed on the road. You don't need to pack two week's worth of outfits for a two-week trip. If you can pack well for a week you can be set for months.
Sending your traveling clothes to the hotel service can get expensive fast, however, with the price rising according to the rate of a room. In many countries you can get laundry done very reasonably nearby somewhere, but sooner or later you have to do some sink washing along the way. I've been trying out some samples for this purpose from Soak Wash that promise to make this effort a bit easier.
Through some magic combination of chemicals billed as "modern care for fine fibers," this detergent is gentle enough for delicate fabrics like knits, lingerie, and silk. Here's the novel part though: you don't have to rinse it out. "When you soak your items, the dirt and detergent comes out in the water and what is left in the item evaporates. When you squeeze out the water, you are left with a hint of fragrance that dissipates over time."
I wonder if this residue will build up over time, but it did leave the clothes smelling nice in my road trip test. You can pick from three fragrances: flora, aquae, or citrus.
The largest size is meant for the home and and the middle one is only okay if you're checking a bag. Thankfully there are small 6 ML packages that are lightweight and are easy to toss into a cosmetic case.
For info on where to buy it, see the Soak Wash website.