Different between Arduino Duemilanove & Arduino Mega

I want to ask about the pins on boths devices.
Is that Arduino Mega has all of the pins of Arduino Duemilanove and more than that?
It is because I now have Arduino Duemilanove. And I want to connect with a accelerometer, cam, and a sd card board.

Cam : C3088
http://courses.cit.cornell.edu/ee476/FinalProjects/s2009/pc389_fs256/pc389_fs256/c3088.pdf
Accelerometer: ADXL 345
http://www.analog.com/static/imported-files/data_sheets/ADXL345.pdf
SD card board:

For connecting the accelerometer and sd card board, the Arduino Duemilanove is quite enough for the pins but not for the cam.
Anyone can give me some suggestion on Arduino Mega? Can I use the same code for boths device?

Yes. There are different names for things, like Serial1,2,3,4, where there are more of them supported by hardware, but otherwise yes. The Reference section has details of the exact names used.

CrossRoads:
Yes. There are different names for things, like Serial1,2,3,4, where there are more of them supported by hardware, but otherwise yes. The Reference section has details of the exact names used.

How about the code for programming?
Because I type some code for the Arduino Duemilanove.
Can I use the same code (may be need to change the address) for the Arduino Mega?

Yes, the rest of your code will be the same. The only difference is for the things where there is more hardware: Serial lines, IO pins, etc. All your variables & functions will port right over.