My interest in anime and manga is largely a solitary pursuit that consists of me watching copious amounts of animated TV shows and answering questions on this site -- I don't really collect merchandise much or go to conventions . However, in the past, I've missed at least one convention that I would have liked to go to, on account of the fact that someone who had been involved with a few series I really like spoke there.
One problem, in addition to my lack of interest in looking through guest speaker lists early enough, is probably simply that I don't really know where I can learn about ongoing conventions. I might know of some small "convention" run by the anime club of a school I might be affiliated with, and, along with that, of one much larger convention in the area. However, I only know of these via word-of-mouth, and I pretty much do not know of the approximate times of any other conventions near areas I've lived in. Moreover, if I travel, it'd be nice to be able to have some approximate idea as to whether there are any conventions in the area, so I can see if I might be interested in going.
With this in mind, are there any websites that list major conventions by location and dates? (Bonus points: are there any particular websites that do not just do so for, say, the US?)