As far as phones go, just get a pay as you go phone from Walmart, verizon probably the best coverage,and you can get cards with plans to call home cheap. Internet, most places you can drop onto a wifi, otherise a few of you may want to club together and get a wireless Dongle, you can get them that will handle about 4/5 computers, BUT they can be expensive and you have to sign up for a year, a webcam is a good thing if you have a laptop and talk via face book, found this to be the best why to talk to home, its done via skype so seems to work OK,and Free
I would not take loads of clothing as clothing is cheep in the US, at Walmart, you just really need to take stuff to keep you going for a month till you get your first pay check, boot, make sure they are new or mega clean as customs can be funny about Dirty boots, Id also bring coveralls as they are not easy to find good ones in the US, handy when blowing down and greasing in the morning, but can get very hot, but then you are clean sitting in your machine all day.
bedding some harvesters will provide this, but if they dont, its Walmart again,Id by proper bedding and 2 sets of sheets, sleeping bag for 7 months not great. take a camera and a BIG memory card, laptops work fine, my want to get a lead to change to there plug style.
Not worth taking big coats as you will not need them till the fall and then you may as well get a Carhartt in the US, they are sensible money.
Basically Walmart will be your friend when in the US, most stops you will do will have one near by
Have a fun summer, its one you will remember.
If you like your Marmite, best take some, same if you like real tea (not ice tea) but to be honest you are best to live as they do.