I am using a recently updated iPhone 4s 5.0.1 and this is how I jailbroke it using Absinthe on Windows 7.

Prerequisites

1.  iTunes
2.  Absinthe
3. Internet connection

This is fairly simple

1. Install iTunes
2. Make sure your iPhone is updated to 5.0.1
3. Run Absinthe as administrator
4. Select Jailbreak
5. Wait a couple of minutes for the program to finish its work (The iPhone will restart, be patient)
6. Tap on the Absinthe icon that has appeared on the home screen of your iPhone device

That is it, your iPhone reboots with cydia installed