A great informative site is greenhybrid.com.
I've owned my 2004 Honda Civic Hybrid for almost 20 months and 44K miles.
Last winter I've averaged about 60MPG and this summer mid-upper 60's. (Miles driven/gallons used)
I get 850 to over 900 miles to the tank.
Majority people get upper 40's to lower 50's. My commute favors MPG and I take advantage of it.
This is a link to the data of most of my tanks since new:
Please let me point out some more common points of hybrid confusion.
I'm referring to the Honda system, which is vastly different than the Toyota Prius. They deliver about the same MPG. It is more difficult to hypermile in the Toyota system. If you already know these points, just excuse.
1. Except for gasoline, they are completely self-sufficient. We don't recharge on the power grid... there is no plug even if we wanted to.
2. Hybrid batteries are an advanced Nimh similar to your notebook computer; the 144 D-size batteries collectively weigh about 80lb and take up about 2 cu. ft. of space. These batteries are recyclable, and are not listed as a toxic item according to the EPA. The computer system intelligently handles all battery charge level, except braking regen.
3. The primary concept of the electric motor isn't to improve MPG, but to bring the performance up to a reasonable level.
4. The size of the ICE (Internal Combustion Engine) is main reason we get the great MPG. Curb weight is just under 3Klb, and has a 1.3L engine.
ICE is tricked out with VTEC, lean burn (Cuts mix ratio in half) and shuts down cylinders if they are not needed, such as while cruising.
5. Accelerating 0-60 is about 10 seconds. The electric Assist comes on proportionally to engine load. ICE and electric work collectively. Electric assist is off unless pulling.
6. My car will not drive on electric power alone. One good point of that is if the hybrid system fails I still drive the car. (Vs Toyota system)
7. Recharging the battery primarily comes while driving & coasting. Regen braking is over-rated and accounts for about 10%. If the battery is a little low, the drag on ICE is extremely light, and is recharged in 1-2 of miles. If the charge drops below about half the recharging drag is more, and drops the MPG by 5-7 for a couple of miles.
8. My CVT auto-transmission has no gears to shift through. It uses a metallic belt that runs over 2 variable diameter pullies. The computer determines load, engine speed, Assist and sets the ratio for optimum MPG.
9. AutoStop shuts the car off in most conditions at the stop sign. I'll drop 1-5MPG if the engine just runs. Starting is much different than regular cars. It uses the direct-coupled hybrid motor to spin the engine at ~1000RPM and is as smooth as if it had never stopped. It also has a conventional starter that is used if the pack is flat, or needs to be jumped off.
10. A few more things: The HCH looks like a regular car. They blend in with all the rest. Other MPG improving items: electronic PS eliminates engine load, it has no PS pump or alternator, specially designed alloy wheels and low rolling resistance tires, special air-directing front cowl, underside panels reduce drag, heat rejecting glass so the AC isn't used as often, etc etc etc.
Honda has just released a press report that the '06 HCH is redesigned with both higher performance and higher MPG. Specs are yet to be released.
Some other hybrids:
Ford Escape is the first hybrid SUV. Ford also has the Mercury Mariner Hybrid SUV. 3 Other Ford hybrids coming.
Toyota has recently displayed a new FTX full-size hybird V8 pickup truck and a FJ Cruiser sport SUV hybrid.
Lexus has their RX 400h hybrid SUV, also to release a new GS 450h hybrid high performance sedan.
Hyundai USA is due to release its Portico sports car v6 hybrid car.
How about a Mercedes S-Class Hybrid? Coming soon.
The 255HP Honda Accord Hybrid is very nice.
All the power of a 6 cyl but 4 cyl economy, the most powerful Accord sold today.
Many military trucks are going hybrid for up to 20% better economy:
Last year alone I saved almost $2,500 in fuel cost over its replacement- a '94 Dodge Spirit that did 17MPG (Based on $1.85/gallon and 32K miles and 60MPG)