Last Sunday I had 17 parties tour my open house. Some of them are potential buyers of that property, some needed more bedrooms or a lower-priced home, and I will be working with all of them. Of course there were a couple of lookie-loos - people who just look at open houses for a hobby and have no intention of buying anything, but that's okay too. They might know someone who's looking.
I've heard all the naysayers advising against open houses, but I have had good luck with them and anyone who is turning down any marketing technique right now will have only themselves to blame if they are not getting any action.
Of course, much of the success is in listing your open house on Craigs List or some similar popular site, making sure the house is clean, uncluttered, and bright and inviting. The agent should be engaged with the guests, but not pushy. Laugh and chat a bit about the house, point out any features that are especially nice, and ask if they are looking for something in this area, this size, this price range, etc while you chat. If you are friendly and can offer them something, they will usually be warm and outgoing with you. It's an old saying, but very true, that people like to business with people they like.
I have attended open houses where an agent pounced on me and made me nearly want to escape from them. I have been to others where the agent never spoke to me. There is a lot of room between, and that is where you make friends and find people who will want to buy from you. If you are the listing agent, you can be the factor that tips them to your listing instead of another. It is all in the presentation.
If you get their name, address, phone number and email address, you can follow up and keep in touch (not always with just sales calls, but maybe info on local events - pumpkin patches at this time of year for example) and although they may keep looking, they may come back to you if you are the one they have befriended.
What has been your experience?

I also think that they work. About 2 years ago half of my sales in one year were from opens. No they did not necessarily buy that house, but with follow up, I end up finding them another house that is more suitable and then listing and selling theirs. My previous broker had a statistic that approximately 80% of people who would walk into an open house would buy a home within the next 6 months. Craigs list is good to advertise them on, also realtor.com and lots of signs and balloons.
Thanks for the craigslist idea. I'm holding two opens this weekend and I've listed both on craigslist, yuvie, and zillow. I chose them based on their location...hot neighborhoods and close to a main road. I'll bring the paper and hope not to get through a single article. In fact, I've had more success with my opens than call time (probably because I hate call time)
Susan, If open houses are working for you, keep at it! I have open houses nearly every weekend, attendance is up and down, I haven't had 17 parties through 1 open house all year, good for you.
The 'success' of an open house is dependent on your definition of a 'successful open house'. If you are looking for buyers to work with, open house can be successful. If you look to open house as a way to sell the property that is open, statistics, over many years, are very consistent, open houses account for less than 5% of marketing efforts that result in the sale of the property open.
I will continue to have open houses, as you mentioned, we need to utilize as many marketing techniques as we can in this challenged market. The increase in traffic at open houses at this time of the year is the pre-holiday season open house grand finale.
Naysayers are everywhere, in life, and in all professions. If there is a 95% chance of selling a property through other marketing efforts, why do we have open houses? Because we choose to. Is there something wrong with that?