uDig would probably meet your needs just fine if you can work within the RCP framework. I don't have any experience with uDig or NASA World Wind, but if you need to put the map features in an existing application, NASA's World Wind Java SDK is another option. It is extensible and supports industry standards for geospatial data. They have an informative wiki here. I first saw NASA World Wind at JavaOne 2007 and it doesn't look like the Java SDK has really taken off nor does it look like the .Net version is seeing a lot of new releases, but it could meet your needs if they are basic.
