For those who have been otakus for a while now, you may already know this site. For the new otakus, I think you'll find it very convenient.
It shows some conventions around the world, and even pinpoints them on a world map. However, not all conventions are shown. I know for a fact that there are anime conventions in Asia, but they don't show them on the site. Even though this may be the case, I still find it a very reliable source.
Through this site, I found out that there will be one coming soon, on March 19 - 20: The Toronto AnimeCon, which happens twice a year. One in March, and one in December. I'm still debating on if I should go or not.
I hope this post helps some otakus out there looking for a convention near them. Have fun, otakus! I know you will, because I did!
Anime North 2010 - People heading for the Dealer's Room