No matter which page your visitor enters through, the look and feel should be consistent with your other pages, and the surfer may not even notice that the domain name has changed from one section to another. You will have the benefit of an additional default or home page for each of your domains, and each area of the Web site gains the benefit of the targeted keyword appearing in the root domain.
Try to select and register domain names that include your targeted keywords. For instance, if you are targeting "whitewater rafting" and you find that "whitewaterrafting.com" is taken, you may be able to register "white-waterrafting.com or "white-water-rafting.com." Be creative! you will find a way to register a domain name with a keyword or phrase in it.
Expect that your hosting provider will not add a domain name for free. You will be looking at $25 per domain name per month, at least, even if you are only putting up static informational pages. But this additional cost is well worth if for the high rankings it may generate.