Panasonic's FZ35 with its measly 18x zoom was due for a refresh and, well, it looks like Panny thought breaking it into two models would be best.
The FZ100 is the top-of-the-line model:
24x f2.8-5.2 25-600mm-equivalent lens
14-megapixel high-speed MOS sensor
3-inch 460K-pixel rotating LCD and an electronic viewfinder
Built-in stereo mic
Port for an optional stereo microphone
Accessory shoe for an external flash
Burst shooting at 11 frames per second at full resolution for up to 15 shots
Full HD 1080p movie mode recording in AVCHD at 30 frames per second at up to 17Mbps
$499.95 available in late August
If that's more camera than you need, but you still really want that lens, there's the less capable FZ40. For $399.95 (also coming in late August) you get the lens; a 14-megapixel CCD sensor; a fixed 3-inch 230K-pixel LCD and an EVF; a 720p HD movie mode recording in AVCHD Lite; built-in stereo mic; and Mini-HDMI output.
Because of the sensor change, you lose all of the high-speed shooting features, and there's no external flash or mic support. On the upside, you gain a CIPA-rated battery life of 580 shots compared to the 410 shot-rating for the FZ100. There are other differences as well, but that's the gist.
I generally don't get excited about megazoom cameras, but as bridge cameras go, these look pretty good. Can't say I see the need for two fairly pricey models with the same lens, though. I would've rather seen Panasonic rework the FZ35's lens into a budget megazoom.