I machine quilt on a regular machine. I've made several full sized and queen sized quilts this way. In the past, I just stitched in the ditch - stitching a straight line along the seems of the blocks. I've recently undertaken free motion quilting.
The hardest part, for me at least, is supporting the weight of a large quilt while trying to get the fabric roll through the regular sized arm and keep it from pulling on the opposite side. There are a few things that can make it easier. An extended quilting arm is great. Lots of manufacturer's sell these or include them with the machine.
You can also buy them custom made for your particular model.
Here' s a link for custom tables:
http://www.allbrands.com/products/abp03522.html
Another way to get great support is to have your machine in a sewing cabinet so that the arm is level with the top of the table. This way the entire table acts as an arm to your machine.
There's also a way to make your own extension table out of foam board.
http://www.youtube.com/watch?v=yAS25v3ZTk0
Having a good pair of quilting gloves and clips to keep the roll together help lots, too.