OK folks, I guess the ideas are pretty much exhausted. In addition to what I mentioned above, this is what I think I'll be using for hands-free when I'm not carrying a headband for my light:
Collar Clip:
As AlPal mentioned above, I've also been clipping to my shirt collar, under the ear, weight supported by your shoulder. However, this originally only worked well with collared shirts for me, which I rarely wear in warm weather.
Last night I finally came up with a way to use it securely on T-shirts. First clip (bezel down clip) your light to your collar pointing 3 o'clock down your shoulder, then roll the light slightly and tuck the tail under your collar. The weight of your shirt holds it in place quite well.
String Sling:
This I'll use for when I'm running my light for hours straight, like camping - sometimes I just don't like wearing a headlamp on my head. You can also wear it around your neck if your using your hands a lot and want to eliminate the arm shadowing - light under your ear again and you need a collared shirt as a snug cord doesn't feel too nice against bare skin. If anyone is interested in a great slip/grip knot, let me know.
Finally, there's the business card lantern attachment, which I quite like too (full thread linked to above):