Last Christmas, my wife bought me a Sigma 10-20mm wide angle lens. Unfortunately, I had some problems with it and ended up sending it back. I replaced it with the Nikon 18-200 that I use as my primary lens so we have not had a wide angle option between the two of us... until just recently. I purchased a used Sigma 10-20mm from a friend and have been very happy with it.
Since I started in photography a few years ago, 18mm was the widest perspective I've had available to me until the purchase of the Sigma 10-20. I have to admit that the way my style has developed over the last couple of years, I actually find it difficult to compose an image with such a wide field of view (above image is at 14mm). Like anything else, I guess I'll just need to get out there and practice some more :-).
What's the widest lens you have in your camera bag? Any tips on "shooting wide"? Care to share some examples links?