Part A is free for the vast majority of people.
The Part B monthly premium, again, for the vast majority, is $104.90 per month this year. $147.00 is the deductible for part B.
For the original poster, you should contact SSA to sign up for part B if you are within 3 months of the month you want to quit. You will have to sign a form, and so will your employer, to prove you've had coverage since age 65 - that way there's no increase in the monthly premium for not enrolling at age 65. Just call the SSA 800#, or make an appointment with your local office. I highly advise not just walking in, but it's your time.
As far as a supplement, the links above are good. All the states around here also have a state program called SHIIP - Seniors Health Insurance Information Program (if your state has it, it will be in the phone book or online) I've heard great things about them in NC & VA. They're not there to sell you anything, which is a definite plus.
One last bit of unsolicited advice, since I won't be viewing this thread again. I understand that people like to ask questions where they are comfortable and also that what other people do are none of my business. But I will never understand, given the wealth of information available today, why people get information about x from place y. Yes, there are many intelligent and knowledgeable people here on a wide variety of subjects, but every time I see a thread about something I know a little about, at least half the replies are dead wrong, to be charitable. After all, you wouldn't go to Medicare.gov or AARP to ask about Smith & Wesson's, would you?
It is still the most affordable coverage I've found and everybody accepts it. Medicare ain't all it's cracked up to be. Damned government. 
