Clothes, definitely! I have to try them on. I've broken down and bought them online and lost every time! Live and learn, for some reason the clothes lose a size or two in the mail, it's crazy!
I have bought food online because it is superior quality compared to supermarket food. I have bought organic fruit and veg online quite a number of times, and it's far better quality than anything I can get in the supermarket. I choose not to buy shoes online. I have once before bought a pair on eBay and they were ever so slightly too big for me. This was pretty annoying as I bought them in the size that I would usually try on in store. I think it's because the size differs slightly depending on the shape of the shoe and the brand also.
I'm kind of weary of buying meat like poultry and beef. Who really knows how long it has been out before they ship it out to you.