This web site presents a list of continuous integration tools both open source (Jenkins, Hudson, CruiseControl, etc.) and commercial (TeamCity, Bamboo). Today the trend is more to continuous deployment and devops with a process that does not only build a check a new software release but also deploy it to target platforms automatically. However, continuous integration is still an important concept for Agile teams that deploy production releases less frequently and is also the beginning steps to reach a continuous deployment stage.
Martin Fowler defined Continuous Integration as a software development practice where members of an Agile team integrate their work frequently, usually each person integrates at least daily – leading to multiple integrations per day. Each integration is verified by an automated build (including test) to detect integration errors as quickly as possible. Many teams find that this approach leads to significantly reduced integration problems and allows a team to develop cohesive software more rapidly.