Canon makes its' own sensors. Nikon doesn't make most of its' sensors, many
are Sony (D50/70/100/200) and a few have been Kodak.
You can look at reviews of specific models and they will generally identify
the semsor manufacturer. DPReview lists the sensor manufaturer in it's
specifications.
Tom
A friend of mine swears that Kodak makes the CMOS full frame image
sensors for Canon. He says that Kodak's image sensors are the best in
the world.
I always thought that in the EOS DSLRs the image sensors are made by
Canon. The only definitive info I can find is in the 20D White Pages
