When I was first given a camera as a kid of about 11 or 12 years old, I was told not to take photos into the sun. Now I do it often and I must admit, digital photography helps you do this successfully as you can check the exposure and results immediately. Taking photos into the sun is useful for portraits as your subject is not squinting because the sun is their eyes (it's behind them!) and it can also give a great halo effect from back lighting them. Sometimes though, I just like to use the flare effect from the sun on the camera lens as part of the photograph. The rainbow effect can really add to an otherwise ordinary scene.
During the last snow I set off with my camera to capture some snowy scenes. I was walking through a wooded area and turned to see this scene (click on it to see it larger):
I was struck by the effect of the sun shining through the snowy branches and before I knew what I was doing I had raised my camera to my eye and was taking the photo. No filters were used and the star shaped flare of the sun is exactly as I saw it on the day. It has become one of my favourite captures.