teamcity-plugin- an empty plugin, includes both the server and the agent plugin parts
teamcity-server-plugin- an empty plugin, includes the server plugin part only
teamcity-sample-plugin- the plugin with the sample code (adds a "Click me" button to the bottom of the TeamCity project Overview page)
Different released versions of the TeamCity server API are listed here.
Here is the Maven command that will generate a project for a server-side-only plugin depending on 10.0 TeamCity version: