THIS IS THE SIMPLEST OF ALL METHODS TO HACK YOUR PHONE & SIGN ANY APP
Quote:
Update: 17-MAY-08
I have updated the root cert file 00000001.rar and now it includes both - Leftup & BiNPDA certificates. This means that from now on you will not have to sign any BiNPDA release before installing. 
This also saves you from the trouble of installing it manually as described HERE and also in their release NFO files.
Big THANKS to FCA00000, Leftup & Zorn for making this possible...you guys rocks
PREREQUISITES:

Install the
SignSis v1.03 Repacked.sisx attached to this post on your phone.

Install X-plore if you don't already have it installed. You can get it from
HERE.

Press
0 in X-plore to bring up the settings dialog and ensure that
Show Hidden files &
Show system files/folders are enabled.

Also ensure that in Application Manager,
Software Installation is set to
All and
Online certif. check is set to
Off
STEP 1: LET'S HACK YOUR PHONE FIRST

Install ROMPatcher from
HERE

Open ROMPatcher and select
Disable caps from
Options menu. Then exit from it.
STEP 2: FINAL STEP TO SETUP YOUR PHONE TO SIGN APPLICATIONS

Copy the
00000001.rar file to your phone. In X-plore, browse to the file and open it.

Then press
4 to extract and select
C: as destination.

Now browse to the file
C:\resource\swicertstore\dat\00000001. Press
6 & enable the
Read-only attribute for it.
All done! Now you can sign any unsigned app and install it.
TO SIGN ANY UNSIGNED APP USING SIGNSIS:
- Open SignSIS and select unsigned
SIS file by pressing middle joystick button.
- Select
Selfsign from
Options menu.
- The signed file will be placed in the same folder with a
SISX extension.
To sign your apps on a PC, you should use the cert & key from Leftup_CertKey.rar with your favorite signing tool.