I have always a problem to remember when the next big tech event will start.
To help, I created http://eve-c.org/.
I started by adding all big tradeshows I know and I will add upcoming events and announcements when and if I get their dates.
I'll try to add some kind of community to submitted events in the future, but for now, I have to add them by myself.
If you have feedback or events, please let me know. And maybe you add the site to your bookmarks.