I am (relatively) new to cycling, bought a craigslist road bike a couple of years ago to see if I liked it (which I did), and by the end of last summer I decided it was time to upgrade (2011 Trek Madone 4.5 wsd). Now I've registered for the MS bike ride this September in Alaska, so I'm trying to figure out what accessories/gear I need.
We still have snow here so I'm hoping to do get some must haves ready before the snow melts. I've got the basics (bike computer, gloves, 1 pair of shorts, helmet, shoes, etc.)

But I'm looking for specific recommendations of things that will come in handy as I train to do 110 miles in one day (and 50 the next).

Bike shorts? Anyone have any favorite brands that are affordable? I know I'm going to need a few pairs...
Anti-chaffing cream? (Is there something like this I may need?)
Tool Kit?
What else am I missing?

I'm just hoping to get a list together of "must have" items, along with maybe some "may need/optional" items to buy later on. The cheaper, the better, as I've already spent most of my money on my bike
Also any advice of good websites where I may be able to find bike accessories at affordable prices would be greatly appreciated!
Thanks so much in advanced for everyone's help!
Jenny