from my experience, I'd recommend CCD over CMOS - it's the sensor used to take the photo. CCD works better in low light but consumes more battery power. CMOS is cheaper to produce and is used in web cams and low end mobile phones - the pictures arent as crisp and in low light you might get no picture at all!
I saw a newpaper ad for a £500 canon
http://www.canon.co.uk/for_home/prod..._10d/index.asp
and I was surprised to see it's CMOS so maybe CMOS has been improved but personally I wouldnt buy any until I've tried it in a shop and tested it in low light.
http://www.dpreview.com/news/0407/04...epixs5500z.asp
4.0 million effective pixel conventional CCD sensor - sounds ok to me. note that effective pixel means the sensor is true 4 mega pixel. some cameras advertise as say 4 mega pixel but the sensor is perhaps 2 mega - they use computing power to make the picture appear 4 mega pixel.
see here about interpolation:-
http://www.photobanter.com/showthread.php?t=5859