Ok - so this may not be something you will use for your everyday Real Estate Open House or Broker Open, but I wanted to mention a site that has helped me focus on my day job by coordinating and organizing some of my personal events. I'm a religious user of http://www.evite.com/. I think I discovered it about 6 years ago and probably use it AT LEAST 30 times a year. Not saying I'm super social (ok - maybe a little bit) but my colleagues and friends do have quite a few get togethers. Whether it's a http://www.tastefullysimple.com/ party. GirlZ Night Out, Baby or Briday Shower, New Years Eve Gathering...I use evite.com and it is such a lifesaver!
As you can see below, they have many different topics and background to choose from. You send out the evite from the site to as many people as you want. The site keeps track of responses and also sends out a reminder to attendees a day or two before for you. The best part, if it's something like a camping weekend, potluck, poker game, etc...you can write a list of what is needed and guests not only respond that they can come...but they can also select what they want to bring. It's great. Below is a sample evite.
I hope some of you find this site useful. Again, if anyone knows of other similar sites that you find to be even better...I'm all ears. To date though...I've found no comparison. Evite is a timesaver and lifesaver. Enjoy ;)