I'm currently waiting for my student visa to come back from the LA Consulate. Their processing time is running about 10 days right now, or so I was told on Friday. I'm hoping to have my stuff back by the end of the week. I was nervous about it but I have absolutely no reason to be.
The britainusa.com website has the best descriptions of the types of documentation you need to send in. Passport, pictures, letter of acceptance from university, proof of financial stability (bank statements or student loan paperwork), proof of US Immigration status.. all original documents. I sent in a thick packet. Good luck!
Oh I forgot to add.. as of April 2004, if you are enrolled for less than 6 month course, no need for a visa. Anything longer than that requires a visa. Techincally, you will apply for a 6 month visitor visa and a 6 month student visa. At least that was how mine was and it was done automatically because I applied with fastrack.