what to bring
First, of course, read through the Participant's Guide. That will give you a more thorough brief.
Then, figure that everything you REALLY need will either be provided, or be available in the store.
You may still want to bring some clothing that is a little better than what is available here - especially gloves and glove liners. But that shouldn't be too important during the summer . . . the provided gloves aren't generally a problem until you get to temperatures colder than -20F - which they WILL get to at Pole and some of the field camps.
Fortunately, the station store at Scott Base (two miles from McMurdo Station) has a decent selection of gloves, if they can keep them in stock.
Boots: surprisingly, the high-priced boots are often the worst here, as the normally higher-quality soles freeze up and become slick in the cold - but again, not a major concern in summer. The gold standard in American boots - Redwings - are particularly treacherous down here.
Bring a camera. Some flash memory cards are sold at Scott Base, but if you want to be sure you have the right ones, bring them yourself - and a USB card reader.
Food - is provided, and you may not have many opportunities to cook your own, so you might want to bring a few items but don't overdo it. If you have any specific questions about what is available in the store, let me know.
Books, DVDs, CDs, etc - plenty of titles are available in the library or the store at no cost - but the selection - though reasonably large - is still limited, so if you really want to be sure you have it, bring it - and maybe you'll want to donate it when you leave.
I've just asked for comments from a friend, and he points out that we have plenty of washers and dryers, plus the air is very dry, so you won't need as much clothing as you might think. That said, your own fleece tops and bottoms are still good, and the program no longer provides a base layer. I personally would suggest merino wool for the base layer.
He also suggests miniature speakers (like what you might have for a computer) for an ipod or the like, and that can make sense for McMurdo, but headphones are still a must - especially at Pole and, I'm guessing, at field camps, where the walls are NOT soundproof.
Can't think of anything else at the moment. Everyone tends to bring too much stuff the first season, until we figure out what we personally need.