I have spent 15 years working on various listings magazines and on-line listings. Others are better able to comment than I am on the technology but I would make the following points:
1. There are a lot if half baked listings sites around. To get and keep the visitors you need to be focussed and authoritative.
2. Promoters don't seek out new publicity channels, you have to sell your site to them. You have to regularly go back and ask them for updates.
3. I have yet to see a successful user updated listings site.
4. New promoters come on the scene all the time. You need to know enough about your topic, and to be well enough known in that community, to find out about them and get in touch.

To have the punters recognise your site as the authority for that topic takes a lot of steady graft.

The other thing is that if it takes off you will get a lot of repeat visits. Repeat vistors tend to be ad blind. I actively told visitors that if they wanted to keep getting listings then they should support us by making their Amazon purchases through our affiliate link. That usually paid marginally more than Adsense.

The Yahoo! homepage is a good example of what you're describing. A set amount of content is automatically displayed and logging in allows for customization to an individuals liking. It's a proven method of converting visitors into repeat visitors.

To accomplish this round up all of your data sources, either via data feeds or by collecting the data into a database, and the rest is simply a matter of displaying that information in a way that accomplishes what you want.

When you have that done you can add more features, such as member accounts, and entice people active in the field to provide information by making it simple and rewarding to do.

Before you start working on this project you should set some goals. If making money is the primary goal a site doesn't need to become viral to be profitable. If being the top site on the subject is the primary goal becoming viral is more important. Your goals dictate quite a bit about how you should approach the project.