I shop online for several reasons. One, being that my personal style is not often found in my size, second, I have limited transportation to get to regular stores. While Amazon.com and Ebay have a good selection of clothing in all size ranges, it is very rarely in styles I personally like. However if you're a person who is more into regular fashion than the off-beat, they should serve you well.
Sometimes I also use JCPenney online, though that is becoming rare as I find their size chart, unless listed for a specific brand, tends to be inaccurate. According to them I needed a 2X in a coat and a couple of shirts and I ended up having to exchange it for an XL, and I might have even been able to get away with a large in the shirts. For some reason they're still using the 50's size chart, when women wore girdles. So if they're just using the regular, non-specific size chart, add 2-4 inches to the item in the waist (in the waist, not anywhere else apparently) and that's really the size you'll probably be in.
I have an inverted triangle body shape, which means I'm broadest in the shoulders and bust and my waist and hips are the same size, even if both are toned. This is different than an apple where the waist is same size or larger than both hips and bust. So shopping is terrible for me anyway. I usually just end up with small boutiques and end up custom ordering something to my measurements.