I have been considering a new Lens for my Digital Rebel XT camera as the standard EF-S 18-55mm lens is good, but it doesn't always do spectacular for indoors shots (which is where Dragon*Con is held).
I narrowed mo choices down to the EF-S 17-85mm IS lens and the EF 28-135mm IS lens; both of these have a larger opening lens than my current lens (72mm vs 58mm) and both have optical image stabilization (hence the IS in the title). In addition, both of the ones I am looking at have ultrasonic motors (indicated by USM) that allow manual focusing without having to turn off auto-focus...
I decided on the later lens as I find myself doing more 'zoom' shots than panoramic shots. The 17-85mm lens is also an EF-S lens designed for Canon cameras with a 'short back focus' body- the inner lens goes into the camera a little deeper to accommodate a smaller CMOS sensor; this will work with my current Rebel XT (or the newer XTi) but not with some of their higher end cameras (like the EOS 5D) and I want to keep my upgrade options open! (my next step is probably the 30D- which will accommodate the EF-S lenses)
I found a nice deal on eBay (about $50 less than a new lens from Amazon) and I received notification that it shipped out on Monday via USPS Priority Mail- so I should have it by Friday! (and in time for Dragon*Con!)