A number of people have asked what lens I used to shoot the bear photos (since we really weren't that close), so here you go. I was using a Sigma 120 - 300 lens that was on loan to us - the full name is the Sigma APO 120-300mm F2.8 EX DG HSM. I was very happy with the performance of the lens - very sharp photos even at a distance and low light. Yes it's large, but it came with it's own carrying case so getting it to and from Alaska was painless.
More details on the lens here