Jenkins
Open Source
Jenkins is a self-contained Java-based program, ready to run out-of-the-box, with packages for Windows, Mac OS X and other Unix-like operating systems.
JetBrains TeamCity
Free Personal
TeamCity is a Java-based build management and continuous integration server from JetBrains.
Concourse
Open Source
Concourse is a pipeline-based CI system written in Go.
Buildkite
Commercial
Buildkite is a CI and build automation tool that combines the power of your own build infrastructure with the convenience of a managed, centralized web UI.
Buildbot
Open Source
Buildbot is a software development continuous integration tool which automates the compile/test cycle required to validate changes to the project code base.
Compare Hudson with alternatives
Compare JetBrains TeamCity and Hudson and decide which is most suitable for you.