There are too many robotics related websites to catalog them all. Here are few of them...
IEEE Robotics and Automation Society's Technical Committee on Service Robots website contains a page dedicated to Agriculture & Harvesting Robots, with many links to related activities around the world.
Arrick Robotics's website has a long list of robotics clubs. One of those, the San Francisco Robotics Society of America has a particularly interesting website.
Robots.net, Robot Gossip, and GoRobotics.net are robotics news blogs.
Artificial Intelligence News, just what it says it is.
I only plan to cover developments which are at least plausibly related to the application of robotics to crop cultivation, except perhaps as a bit of news is so compelling that I can't help but mention it.