We've been doing First Lego League since 2007, with only last year off. Bit-Boy is feeling done with FLL, and has asked "What else is there?" Here's what I've found so far.
BEST, and it's local affiliate Rocky Mountain Best have a season that run in the fall like FLL. Like so many things in Colorado it seems centered around Denver, and I haven't had any luck getting them to return my emails to get more info about getting started here in northern Colorado.
Lawrence Tech sponsors Robofest, which looks intriguing. Their comparison with FIRST competitions exaggerates the cost of FLL, so I don't know if all their other info is correct. Also, it looks like it's (quite reasonably) centered around Lawrence Tech. and I don't see any affiliates local to us. I wonder if we could convince some one else to start one up?
VEX also has robotic competitions. It is no longer used with any FIRST programs. Locally the Thompson School District still supports and hosts VEX competitions.
And of course there is always FIRST. In addition to First Lego League, there is the FIRST Tech Challenge and the FIRST Robotics Competition. FLL we already have done, it uses the LEGO Mindstorms kit.
As far as I can tell the FTC is affordable. It also uses the Mindstorms kit plus add ons like Samantha WiFi Module and seems to allow other programming like RobotC. This makes it much more do-able for a home based team than the FRC.
FRC requires 2 engineers, 2 adult volunteers, access to a machine shop, and a $6500 recommended minimum to start a team. If my kid really wants FRC, he's going to have to go to the only local high school that supports it.
At the moment FTC is looking like our next direction in robotics. I'd love to hear about any other resources out there, and about any of your experiences with these or other robotics programs.