I have the Sauder Sewing Desk that Walmart carried a few years ago. I wanted a flat surface to quilt on so hubby cut a hole in it and put a shelf below just at the correct level to keep the sewing machine bed flush with the top of the desk. I love how it was customized for me but now it is too low so I've got to get hubby to help me put it up on some type of risers. I use it like it is but my back gets very upset with me if I sit & sew for more than an hour or so. Here is a link to the picture of it:
http://www.quiltingboard.com/t-43071-1.htm
I also have one of the cheap taller style sewing cabinets that has a spring loaded platform in it so that the weight of the sewing machine is supposed to make it sink down into the cabinet so that the bed is flush with the top. My old mechanical machine does fit inside and can be squished down so that the bed sits flush but my newer, electronic machines are too wide to fit so I would put a book down into the recess and my machines sit on top.