AAA-type roadside assistance
AAA is certainly the best-known of the 'towing insurance' providers in the US, but they may not be the best for you and your motorcycle. Contrary to popular belief, AAA is not really a club itself, but an umbrella organization of local/regional clubs. Each chapter has its own rules, governing body, and fine print. What is offered by AAA will depend on where you live. Make sure you read everything and know exactly what you are covered for before signing up.
One thing is for sure: A regular AAA membership won't cover your motorcycle. You need an advanced level of coverage (at additional cost) to have a motorcycle towed. There are some options, recommended here by your fellow EX250 riders.
Riders of Kawasaki (ROK) premium membership offers towing and fuel delivery. Actual service is through Road America Motor Club. Occasionally they offer a free 1 year membership (such as when you buy a bike). Mine expired a while back and I renewed. Good thing that I did because I ran out of fuel in west Texas. They had one of their members deliver fuel to get me to the next city. It only runs $39.99 for the year. I have been very happy with the service thus far. A distinguishing feature that separates ROK from other services is the preferential treatment at bike shows: Kawasaki test ride priority, gear check, and other stuff.
Markel BikelinE offers road-side assistance with their insurance policies... And it seriously saved me in the middle of Kansas last week. Yeah, umm... don't ask. Free 35 mile flatbed tow, with a small fee after that. I was 15 miles from a dealer, so it was great. It costs me a few dollars a year to have this, and they'll help with a few other things like fuel and such if you run out. I've also been very happy with their customer service and prices. Other companies may or may not have similar programs for bikes.
The American Motorcyclist Association offers MoTow roadside assistance. It is $25 a year for your motorcycle, with an option to add your car(s) for an additional fee. You have to be an AMA member, which is $39 a year. As of May 2010 they were offering free motorcycling towing with the regular $39 membership. I'd rather pay to AMA than AAA. At least AMA is trying to do something for motorcyclists.
Motorcycle Towing Services is recommended (but turn down the sound on your computer). Except for their annoying website, they're a decent company. I'm a member, and I had to use their services once. They did a pretty good job.