Having worked countless hours in emergency rooms, I can tell you that patients rolling into the e.r. vary widely in composure. Some can calmly recount the exact details of their illness. Others can barely remember their name. Providing accurate, concise information during an emergency is crucial. So carrying a brief synopsis of important medical information with you can literally save your life. It can be low tech (written on a card and kept in your wallet) or high tech (an email to yourself, stored in your Blackberry or other personal digital assistant so you can email it to somebody in the emergency room). Trust me: the doctor will not know what "the little green pill" is. You need to know the names of your medications, and the dosages, and how often you take them. I've put together a list of some basic information that you can carry with you; it's not all-inclusive (I've kept it to a single page) but it should be helpful in orienting your emergency healthcare providers (Download file here). I suggest you try to bring a pen and writing pad to jot down details of your illness -- on the way to the hospital if possible; you also may want to take notes so you can remember what you were told by the various health providers you will be meeting. Don't underestimate how discombobulating an emergency visit to a hospital can be!
Because you never know where you'll be -- or what you'll be carrying -- when you head to an emergency room, I highly suggest that you share your medical synopsis with an "emergency healthcare buddy." That person should be technically savvy enough to transmit the information (securely if possible) to the emergency room via email, fax, or whatever new technology comes along.