As someone who has owned a hybrid car for two and a half years, let me be blunt: if you drive your hybrid the way you drove your last (non-hybrid) car, you're not paying attention. Hybrid-electric cars may look more-or-less the same on the outside as other gasoline-only vehicles, but the difference in the way they operate requires changing driving techniques in order to get the best mileage possible.
We've talked before about hybrid driving tips, but now it appears that some of the manufacturers are starting to pay attention to the need to train new hybrid drivers to drive differently. Both Toyota and Ford are taking steps to raise buyer awareness about hybrid differences. Toyota is distributing pamphlets (PDF) with their Lexus R400h hybrid SUVs explaining why drivers may not get the EPA estimated mileage (and what to do about it), while Ford is actually taking engineers around the US to teach people how to drive their hybrid Explorers for maximum mileage. According to a report from one of those workshops, attendees were able to boost their mileage by over 10% immediately.