Installer.app

Installer.app (also known as Installer) is a homebrew application for installing third party applications on the iPhone OS. It can be installed after the jailbreaking process. Installer.app currently runs on firmwares 4.0 and up (and maybe 3.x, not too sure), but version 4 and further will support only firmware 3.0? onwards.

Until version 3 it was developed by Nullriver, and since version 4 it is being developed also by RiPDev. The new Installer is being developed by Infini-Dev, and currently runs on iOS 4 and up.