I'm 66 years old, receive social security and I'm ready to leave the full time work force. I don't have a pension plan but have a 401k with an outstanding loan. My question: From a Human Resources perceptive, is there any advantage to announcing my retirement as opposed to just giving my notice?

You say there is no pension, but don’t menton if there are any other retirement benefits that the company may have, such as health or life insurannce. If not, then it really doesn’t make much difference whether you call your departure a resignation versus a retirement. The only considration in this case may be whether the company treats retirees better, perhaps with a nice retirement dinner in your honor or a parting gift (the proverbial gold watch). In any event your 401(k) becomes available to you as soon as you depart from the company, and so you should think about whether you will want to roll it to an IRA or keep the investment in the company 401(k) plan.