I wear tank tops or sleeveless shirts the majority of the time when not at work. I always have and I don't do it to show off. There comes a point where you just wear what makes you comfortable. You get stared at, you hear the comments and you go on about your business. I have a ton of Under Armour LOOSE GEAR. For those that didn't know, they make loose clothing as well that fits and looks great like regular t-shirts. Their web site is filled with shit. I sweat easily so those help as far as function. I just feel comfortable and I have no issues with my arms showing. I get some comment from someone almost daily about my size so it has really gotten to the point where I half expect it and half ignore it. I try to act as if it is the first time I have heard the same comments, half smile, and move on.
Once you get to a certain size, you are going to stand out no matter what you wear. If I truly cared that much about what people think, I would wear a jacket 24/7 and quit lifting weights. Learn to have more confidence in yourself and you will care less what other people think. Most of it is in your head anyway unless you are really that much bigger than everyone else.