It took much longer than we have anticipated, but the Microsoft Windows version of InstallerApp is finally out. It works on anything from XP to Seven, and requires an installed iTunes. Otherwise, give it a go. License purchased ties to the devices, not the app itself, so it doesnt matter which platform you use - the activation codes will work regardless.
InstallerApp is an application that allows you easily download applications from Installer and Cydia directly onto your computer, and install them to the iPhone connected with USB cable.