UK visa from USA for F1 student

[grisbo]

I am a graduate student on F1 visa in the USA. I am graduating on 14th Dec, 2011 and will be on OPT thereafter for one year. I have a full time job starting in February.
I am planning to visit my girlfriend in UK for about 10 days in the end of December. And I have to apply for UK visa.

I want to know what all documents I need apart from finances, my I20 document. Should I mention to the authorities that I am visiting my girlfriend? or is it too risky. Should I ask her to give me an invitation letter. Or is it better that I just say I am visiting UK for a vacation.

Also, since I dont have too much finances right now. My bank account balance wont be enough to take care of my trip. Is it okay if I mention a friend in the US as my sponsor for the trip. Or is it okay if I mention my girlfriend as my sponsor?

Is there something I should be careful about?

[kabkaba]

Anybody can provide funds for your trip. No harm in mentioning the girlfriend and getting an invitation letter from her.