+1 To craigslist, and kijiji if it is popular around your place, or Used<city>. I'd avoid Cycletrader if they require you to pay for an add (they used to, not sure if they still do. I put an add in my Cycletrader and had the bike sold on Kijiji before the ad ever went up - I never got a call through CycleTrader, so money wasted).
To sell the bike quickly: Give it a real good cleaning, including a wax (on a motorcycle, this takes almost no time, they are much smaller than cars). Take photos of it on a sunny day. Make sure you get some pretty pictures of it (as little in the background as possible, the focus is on the bike), one of the dash showing the odometer, and some close ups of any damage or wear. In the write up list what is new on it, and what still needs work (scraped fairings, etc).
Also, advertise the Katana as what it is - a comfortable sport touring bike, not a race replica. Doing that will attract more of the the guys who want a fast comfortable bike, and fewer kids unable to pay what you want.
Basically, make the ad as professional and honest as possible, and you'll attract buyers fitting that description.