Do you use multiple domain names and park them on your main domain to drive more traffic to your site? Does/will this work?

Mark

It will work, if you advertise them.

We do use different domain names parked on top of our main site. We use them in various different campaigns and different postings/forums. As long as you market them, you'll get the traffic. Google however will rarely rank the 2nd domains, just the primary as it considers the other domains a duplicate content.

Yes it works only if you are promoting them too along with your main domain. But what's the point of having all of them when you can invest the same promotion and advertising for your main domain?

As Conor said above, the main domain is considered primary and all other parked and redirected domains are considered under copied content and add no much value than mere small amount of traffic.
Better to maintain just the single main domain and don't worry about any other parked domains which don't add much value.

I would personally use variety of domain names to create individual site for branding purpose rather than pointing all of them to main domain name.