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.
