Want to install apps for jailbroken iPhones without actually, y'know, jailbreaking your iPhone? There's a…wait for it!…app for that.
Ripdev's InstallerApp (for Mac OS X, with Windows version coming soon) "allows you easily download applications from Installer and Cydia directly onto your computer, and install them to the iPhone connected with USB cable." It also claims to bypass the need to download apps to your phone via 3G or EDGE by downloading them to your PC first, then adding them on your next sync, and that it's safer for your phone's internals than Cydia's dpkg.
And all this for a measly US$7.00. This assumes you're too technophobic — or just plain scared — to pwn your own phone.
OR Ripdev admits defeat to Cydia.