This article in The Observer
is notable for its lack of victim blaming and offering actual useful advice for the aftermath of a rape. Please note that this is from England. Protocols will be slightly different in the US but not much.
What to do if you are raped
Report the rape in person at a police station, Sexual Assault Referral Centre (SARC) or the A&E department of a hospital.
Tell a friend or family member so they can accompany you. Take a change of clothes - you'll have to hand over what you're wearing.
Before you're examined, try not to go to the toilet or have a drink. Don't take a shower or wash.
Keep all evidence, such as condoms and tampons.
Try to tell as full a story as you can. Don't worry if you've taken drugs or are drunk - the police just want an accurate picture of what happened.
Ask if there are facilities for your statement to be taken on video - it can be used in court later instead of you having to go through the whole story again.
Try to get some counselling, either via a SARC, the NHS or privately; it will help you deal with what has happened.
tip o' tha touchpad to Bitch, Ph.D.