N.:
Hi. Well I was just dealing with this topic myself today (out shopping for nursing tanks). I have a 2 year old and a 1 month old. I never really nursed in public with the 2 year old (went into a dressing room or nursed in the car) but I was determined this time around to not have to leave a room if I want to nurse as it is somewhat isolating. Someone else mentioned the Hooter Hiders cover up which I have and LOVE. I'm not confident enough to just whip it out without a cover up of some kind but I've used the Hooter Hiders cover up several times just sitting out in public or visiting with relatives and it works great. It has a strap that goes behind your neck and then the neckline has a stiff section that keeps it bent out so that you can look down at your baby, what you are doing, etc. That was always my problem with just using a receiving blanket - 1) the baby didn't like a blanet directly on their head and 2) I kept having to lift it to see what was going on, readjust, etc.
Re: nursing clothes - I see that others have mentioned MotherWear. I just ordered a cute tank from them. It is a decent (but not awesome) built in bra - I'm a 36DD right now. My biggest rave though is for the Bravado nursing tanks - I just bought 2 today. They have an awesome, really supportive built in bra, they have good coverage so you're not hanging out all over and you could easily just wear the tank alone. They are a bit expensive but its so hot right now I plan to live in them. I got them at Goore's in Sacramento but you can order them online - you'd want to try one on first though because I got a bigger size than I would have thought.
Good luck!