What is your website about? What does it do or provide? Even if it is something completely virtual - such as MMORPG currency or items - you need to have a comprehensive offline advertising campaign in place. Traditional advertising is still highly effective, even for websites and web-based businesses.
Especially if your site deals with MMORPG, games/gaming, and the like, you should hit all the conventions you can afford. And have great-looking cardboard displays on and around your booth/table. Trust me when I say that attending even one of these small cons can increase awareness of your service and/or product by tenfold! The great big ones, not so much; there's no need to even try to compete with the really big guys, unless you already are one of those really big guys.