Azure Dynamics have a series hybrid London-taxi that is performing quite impressively in trials in the city. AC-propulsion have been running a Volkswagen based series hybrid on US roads for a while now too - but neither are available commercially yet.
However, I think Honda will almost certainly go down the series hybrid route at some stage. The problem with their system at the moment is the lack of pure EV mode, which is a distinct selling disadvantage to Toyota's system. BUT, the two companies have a huge amount of pride in their own technologies, and more to the point are bitter rivals that, not to put too fine a point on it, absolutely hate each other, so there is no way on earth that Honda would ever consider losing so much face by licensing the power split method from Toyota. (Ford, in their own research, realised that the whole splitting power thing was just the best way to go with a small battery, so couldn't do anything but sign the agreement with Toyota to use their patents. Same with Nissan too.)
So, to my mind, what is the only way out of this predicaemnt for Honda, saddled with their non-EV mode technology? Installing a bigger battery and going series hybrid. No embarrasing patent problems or meekly knocking on the door at arch-rival Toyota - the first series hybrids were buses designed by Ferdinand-Porsche in the 1920s, so the patents on that whole system have long run out! Will be very good news for those keen on plug-in hybrids, as this constant one-upmanship between the two companies may well be the catalyst required to usher in the next tier of hybrids to the market. As a note of further interest, I've noticed that Honda are forging close links with JEOL... presumably with an eye on their 75Wh/kg ultracapacitors! :wink: