Samsung Galaxy S Plus GT-I9001: How To Root Or Unroot Via Stock recovery
NOTE: This method is for those that are on a completely unmodified phone with a stock ROM and stock recovery, and have never flashed any custom ROM. Those who have flashed a custom ROM on their phones already have root access, so this guide is not for them.
Samsung Galaxy S Plus GT-I9001: How to root or unroot via stock recovery
Following the above procedures, you can root (and un-root) your Galaxy S Plus I9001 using the stock recovery, and use all the root-enabled apps you wish to use. Let us know how it works for you, in the comments below.