I have been shooting with Nikon only for the last 5 years, and just recently decided to buy my first Canon. I opted for the trusty Canon 20D, and got a great deal on a body only. So, I am looking to buy some glass for it. Since my experience is mostly with Nikon glass, I'm not exactly sure what's out there for Canon. I am looking for a nice lens, that I can use in a lot of different situations. Kind of a do-all lens, that I can use for portrait/landscape/nature, and I really only have the money to grab one lens right now, or do an inexpensive pairing. Any suggestions on a good quality, versatile, affordable lens that will work with the 20D?