Check the Reader Developer's Corner subforum of the Sony Reader Subforum, the thread you're looking for is a sticky (so it stays at the top of the list), I'd suggest the Hack Builder thread, as the app in there will let you choose the hacks you want through a GUI (Graphic User Interface, in case you don't know the term

). Just look through the thread for tips on using it, and to make sure you get the most recent version of the tool.