TeamCity is a popular and widely used continuous integration solution by JetBrains, and it's quite easy to configure Karma with it. After you have installed Karma (by following my guide) on your build server, all you need to do is add a build step in TeamCity to start up the Karma test runner. You do this by adding the following command:
karma start --reporters teamcity --single-run
In the "Command executable" field in the TeamCity build step:
That's pretty much it, let me know how that works out for you!