I copied a setup from someone else here - I have a pair of tables (cheap, from Ikea) in an "L" shape, and then my sewing machine sits on a smaller adjustable-height folding table in the crook of the "L", adjusted so that the extension table from my machine is as close to level with the 2 tables as possible. So I have space behind and to the left for quilts to rest. It's great, I FMQ'd a king-size quilt recently and it worked out really well. My only gripe is that the little table that my machine sits directly on has a little bit of a bounce to it, and the legs are in a cross shape so they're kind of in my way. Eventually I want to get a better little table but it's hard to find something in exactly the right height.
For a more temporary solution, I've seen/heard of people using their ironing board behind their machine to support the weight; and/or butting their machine up to their bed for lots of support space.