Actually, my dad got me this magazine "Computer Music" and something else, and both of them came with a CD of just random samples. As for sound banks, I would highly recommend freesound :: home page, all you have to do is sign up for free and you can easily download any sound someone has uploaded. This is more for realistic sounds though, more processed sounds come from different collections of different sample CD's.
Alternatively, you can link each sound directly into a track from the mixer board and add an effect to it directly. Things like reverb, delay, and distortion all come standard with fruity loops. Working from that, there are nearly limitless effect plugins that are available for download all across the internet. These can act as specific or strange effects that work with FL studio directly, increasing the overall feel of your sounds.