From ModMyiFone - Wiki
1.1.1 firmware version users simply navigate to http://jailbreakme.com/ in your MobileSafari browser on your iPhone and follow the on-screen instructions.
using apptapp to install installer.app
a tutorial for windows users
This tutorial will teach you how to:
-Use the AppTapp application
-Install installer.app
System:
Windows XP SP2
iTunes 7.4
iPhone 1.0.2
Programs:
AppTapp
Installer.app (use apptapp to install)
Resources:
A video guide created by Jakeyboy
Step 1
Dock your iphone
Step 2
Download AppTapp
Step 3
Run AppTappInstaller.exe
Step 4
Follow the on screen instructions
Step 5
Choose a iPhone Firmware version
Step 6
The files will be transfered over and your phone will go into recovery mode
-if you click on show details you will see
Step 6
Close AppTapp
Installer.app should now be on your iphone and ready to use.