What you'll need:
-A hacked Samsung i8910 (refer to THIS post).
-Download THIS zip file. Extract it and copy its contents to your phone.
-A file browser on your phone. Here's a pretty good one.
Install turbo_hd.sis(it's in the zip file) to the C drive of your i8910. Don't click on it yet.
Open ROMPatcher and make sure the Open4All patch is enabled. Now open your filebrowser and navigate to C:\Resource\. In here, make a new folder called versions and paste the sw.txt file into this newly-created folder.
Restart your phone. Click on the Turbo HD icon. Done!
What does it do? This hack (created by HyperX and Panagiotis Xenitidis, then repackaged by Wireless) forces the i8910's processor to remain clocked at 600MHz, a little bit like overclocking it. Normally, the i8910 cruises at 550MHz and only goes up to 600 when needed. This will have an impact on your i8910. It's no placebo -- your i8910 doesn't just feel faster, it is faster. Of course, this will likely also have a slightly adverse effect on your battery life.
Note that after a reboot, your i8910 defaults back to 550MHz, so you'll need to click on Turbo HD again after each reboot.
Disclaimer: You choose to use this hack of your own free will. I can not be held responsible if this hack causes any damage to your phone.