Something I'd forgotten about but am now starting to use again is My Virtual Model. This unique web site allows you to enter your height and weight and creates a 3D mannequin that you can try clothing on from a few retailers. You can even upload a picture of your face.
This is my model above, however I selected a face that looks somewhat like mine rather than uploading one.
The upside to this is of course getting to see precisely whether or not those jeans do indeed make you look fat without twisting around into uncomfortable positions under harsh fitting room lights. Just click the "rotate" button!
The downside is that there is a very slim choice as to the make of the clothing. This program, unless you only shop at Land's End, H&M and Levi's (and a select few other) is better for seeing what style of clothing looks good on you rather than the actual piece itself. They do have a "generic" option for each style of clothing available as well as items from a few different brands. It would also be really nice if they could then reccommend a size!