There’s a couple of things you can try:
a) total redirection, which may only temporarily fix the problem but could work: the “crash mat”. When someone comes to the door, the response expected no longer is “rush to the door to say hi” but “run to the mat and crash/lie down” as fast as you can (click, treat). Obviously, you need some helpers and lots of practice. Turn the focus of the “Someone’s at the door!” excitement onto YOU and the oh-so-special food reward (liver works well, and in jackpot quantities). Once that sinks in, you’ll have a dog who thinks that when someone’s coming into the house, the fun part of the whole thing is running to her mat and crashing down for you to come to her and give her the bestest treats in the whole dang world, screw the guests… Then, put her at a heel (you’ll have her total focus, you have the liver, man!) and drill in some polite heel/sit greetings of the guests while they are sitting down and no longer at the door.
b) another option is the Knee-the-dog method. It rarely fails. The dog jumps up, you knee it in the chest – not hard, but enough to surprise it. Yes, it may well fall backwards if it jumps high (one of my aussies is notorious for that…) but it will quickly learn that jumping up is just not worth the effort.
c) a variation on b: keep walking forward right into the jumping dog. Talk about frustrating. You’re doing this jumping up in greeting routine, and you keep falling down, backwards, and being run into, and getting your paws stepped on AND you’re being ignored, and and and! Totally defeats the purpose of the annoying-in-your-face exercise. Dang it! Again, it’s a form of redirection – if the whole shebang doesn’t work, the dog usually starts offering a behavior that might start paying off. The minute she sits, holy hell you better start pouring your attention on her (your accomplice can, too, but really, YOU should be the one doing the praising – remember, YOU should be her focus, not the guests). Reward the behavior you want, and do all in your power to make the annoying behavior totally NOT produce what SHE wants.
d) since you don’t want her to associate a leash to the exercise, consider a “tab” – a small 6" (inch, not feet!) leash attached to her collar, enough for you to have a handle, or using a “handle” collar. Drill a routine for door-answering when someone comes to the door. With an accomplice, focus the dog’s attention on you (food, man, high-value all the way) – again, the idea is to make YOU more interesting than visitors. Since part of her problem may well also be her jumping on YOU, combine this with the kneeing or walking-into-the-dog technique, then the MINUTE her butt hits the ground into a sit, draw your hands up to your chest, reward the sit, praise, lather rinse repeat, get her into obedience-thinking-mode…
Just a few ideas to get you going.