Must haves?

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

Don't skimp on shorts. The right shorts are important for long rides. Personally I like Shebeest Century shorts.

Lately I've been using Hoo Ha Ride Glide for chamois cream. Used to use Chamois Butt'r, which worked fine until I started being allergic to it. Others here like plain old shea butter.

You should carry a mini tool, frame pump, spare tube(s), a patch kit and tire levers on your bike.

You'll want to experiment with foods/beverages/gels etc. for eating and drinking on rides. My stomach usually can't tolerate real food while I'm riding, so I stick with Gu for "food."

You'll also want to be ready for whatever weather you'll be riding in -- windbreaker, rain jacket, arm and leg warmers, tights, whatever's appropriate for your climate (and the climate in Alaska in September).

Other things I carry in my bike bag: pocket pack of tissues, cell phone in a zip loc bag (in case of rain), albuterol (for asthma), chapstick with sunscreen, tiny bottle of hand sanitizer, various sizes of band-aids, jimi wallet with ID, insurance info, credit card and a little cash, Road ID on my wrist.

I use lots of Neutrogena Sport sunscreen SPF 70 and wear good sunglasses on every ride. I can change to lighter color lenses for low light conditions.

In addition to owning multiple pairs of shorts, I have extras of just about all my other clothing so I won't need to do laundry after every ride in order to have clean clothes for the next ride.

you already found the right website!
welcome to TE

NY Biker covered just about everything that you'll ever need. But I'll add one more item that I didn't see on her list...cycling socks. My feet are very picky about the socks I wear...especially on long rides. I'm partial to wool socks, as they regulate different temperatures very well. So you may want to experiment a bit with a few different types (and thicknesses) of socks out there to see what your feet feel most comfortable wearing.

Linda

Oops, I thought she already had socks.

I always match my socks to my jersey. ;)

Wool definitely keeps me feet warmer in chilly temps. I haven't tried wool socks in warm weather (yet).

BTW if you don't already have water bottles or some other way of carrying beverages, you will need one. I carry two water bottles on my bike, which is generally more than enough to get me from one rest stop to the next. For any ride >= 2 hours, I have 1 bottle with gatorade and one with water. I like the Camelback insulated bottles; Polar insulated bottles are good too but the ones I have are too tall for my new bike frame.

You can never have enough bottles.

Thank you everyone for the recommendations.
I actually do own a few pairs of PI socks, but haven't experimented yet to figure out what I like best (yes, I typically just wear these socks as every day sort of socks because I think they are cute). I haven't tried wool yet but will definitely need to try some out. I also have a camelback water bottle/pack that I have used before, and I like it.
I think the hardest part will be figuring out the shorts and tights...so we'll see what I can find out there.
Thanks again!

Wet Ones individual wipes. They come in single packets and are great for getting grease or any other crud off your hands. Hand sanitizer is good too but after a few hours on the bike, stuff builds up. Not to get too gross. :p

Looks like everyone has covered all the important stuff, as far as cheap online buying, I like Price point, Nashbar and occasionally Performance bike. Good luck with the ride.

I too like Price Point, Bike Nashbar, and Performance Bike, also REI. I bought some Shebeest Knickers off Ebay, new with tags, at a fraction of the price. So watch Ebay too. This is an EXCELLENT website.

I found a couple pairs of shorts on bike nashbar that I ordered (along with a jersey just for fun). Love the great prices!
I also went to a LBS and bought my first pair of biking tights...looking forward to a ride on Sunday (assuming the snow has melted by then!)
Thanks again everyone!