There's a wealth of information on the VSRI site:
http://www.vstrom.info/Smf/index.php/topic,3478.0.htmlEssentially there's two cheap mods you can make:
(1) Remove the rear plate on the exhaust and cut off the short 'pea-shooter' pipe that's on the end of the can, then replace the rear plate - this sets up turbulence in the outlet and adds a deeper, throbbing note to the bike.
(2) Remove the rear plate on the exhaust and then drill the can end with a few 1/4" holes - leave the rear plate off - this is effectively drilling out the baffle and will give slightly more power as well as making it sound louder.
Of course, if you get either of these wrong, or don't like the result, you've just screwed your exhaust.