"Kobudo" literally means "ancient martial ways". In the karate world, it generally refers to those traditional Okinawan weapons whose history and practice has been linked to that of karate.
Most Okinawan styles have at least some kobudo/kobujutsu curriculum. In addition, there are at least two major Okinawan organizations whose primary focus is these weapons arts: the Ryukyu Kobudo Hozon Shinko-kai and the Okinawa Kobudo Renmei. In the US there is 'Okinawa Kobudo Association, USA'; the shihan in the US is in Citrus Heights, CA. There may be other US Kobudo organizations.
The most common kobudo weapons (and the ones most often taught by Okinawan karate systems) are: