I've always wanted a rope wall like you find in those well-stocked Iyengar studios. A rope wall lets you do long, restorative downward-facing dog poses. This is fabulous for people with RSI or carpal tunnel, where wrist pain can make long holdings of downward dog painful.
There's a great way to get this feeling without a rope wall, though. All you need is a door that opens into your yoga space and a strap. Belt the strap, leaving it very roomy, then slip it around your doorknobs like so.
Step inside the strap, facing away from the door. Separate your legs so they come on either side of the door, lean forward to place your hands on the ground, and adjust yourself so the belt is taught and the door is holding you in down dog.
This feels so great. The door does most of the heavy lifting, but you can still work the legs intensely, taking the inner thighs back and the heels toward the floor. The relief in the wrists also lets you work more subtle details about the arms, such as externally rotating the upper arms ("hollow the armpits") while internally rotating the forearms. The spine lengthens and the head relaxes down toward the floor.
The best thing about a rope wall, though, is hanging upside down. When you have neck pain or cervical spine injury, sirsasana (headstand) is contraindicated, because it compresses the cervical vertebrae. Hanging from the wall lets you get most of the benefits of the headstand, plus your neck gets delicious traction. With the legs in baddha konasana, you get a nice inner thigh stretch, too.
Inversion tables are too big and expensive. I just found a great alternative, though! It's an inversion sling...
I had to search all over until I found a place that carried this. (Look under "Chairs and Ropes.") Your door needs to be heavy duty, but the front doors of most NY apartments are sturdy enough. A nice way to follow this is with chair shoulderstand, then a long relaxation.