What systems of robust steganography are out there?
The field of research that deals with robustness is watermarking. There are hundreds of techniques to deal with the different existing attacks (resize, crop, recompress, etc).

Currently there is no system that overcomes all possible attacks. But there are some approaches that solve a lot of attacks under certain circumstances.

For example, this is a classic paper for solving RST (Rotation, Scale, Translation) attacks. 

But I think the most robust current methods are based on zero-bit schemes. Check, for example, this paper.

I suggest that you define the most important attacks for your application, and try to find papers that deal with these attacks. But it is quite complicated to implement these techniques for non-experts in the field. 

The alternative is to try to deal with the different attacks by using simple techniques. For example, use a copy of the original image for mark extraction. This keeps things easy. 

Use a DCT transform of the image. Then hide information by modifying the DCT coefficients. You can recover the original DCT coefficients from the original image and the mark from the differences between the original and the marked image.

This resists the resizing process to some degree. If the user makes a crop, use the original image to find the same crop in the original image. Then you can recover the mark as before. The same procedure can be used to deal with rotation.

This approach has many problems, but it provides you with an easy starting point.