Since I should be writing papers, I'm going to limit this post to a couple of quick comments.

I'm glad you're willing to give Anchorage a fair bit of time, but I echo fti's comment that it may be overkill to spend three nights here.

I think you can easily do the zoo in a half a day. If you really want to enjoy it and take it slow, you could probably spend 2-3 hours...otherwise, a little over an hour in the zoo itself is probably enough. (A few other FTers and I did the zoo in March, and we definitely didn't spend more than two hours there, and that was ambling at a very relaxed pace and often spending more time talking than actually looking at animals.)

If you have any desire to do some things outside the city (as has been suggested by some others and as will likely be suggested by me when I finish up school later this week and have time to think and post some more!), a rental car will come in very handy--although if you're coming in the middle of the season, be prepared for quite the sticker shock. If you do want to avoid the rental car and do the bus/shuttle combo to the zoo, it should be easy enough--grab any bus heading down 5th Avenue, which will dump you at the transit center. From there, several bus lines leave and end at the Dimond Center. From memory, I would expect that bus #60 would be the most direct (heading mostly directly south along Old Seward Highway), but since most buses only run once per hour here (every half hour during peak commute times), if you miss #60, it may be better to grab another one leaving sooner (#2, #7, and #9 all go there, IIRC, with probably #9 being the most direct of those three). If you're confident, you can position yourself at an appropriate place on 6th Avenue and catch bus #60 or another one and skip the transit center, but make sure you're west of C street before doing so (I believe bus #60 turns from eastbound 6th onto southbound C). Bus schedules and maps are at http://www.peoplemover.org.

Enjoy your trip!