Here's another tip I found recently about taking portrait shots outdoors in full sun. As Chris mentioned, it's tough except when the sun is low in the sky.
I found a manufacturer of photography lighting equipment that sells a kind of sun screening device, for about twenty dollars, that I plan to buy.
The company is called Photoflex (
www.photoflex.com) and they make a whole set of different lightweight flexible fabric disks that can act as reflectors, filters, etc. The one I think will be most useful is the one that is somewhat translucent.
The idea is that you have someone hold it between the subject and the sun as you take the photo. It lets enough of the light through that the person isn't completely shaded, but it blocks enough sun that it removes harsh shadows and squinting. If you don't have an assistant to hold the disk, this company also sells lighting stands (which I have) that you can clip the disk to.
The resulting effect is shown in the before and after photos I've posted.