Re: line following robot
You don't need color for such a simple application, so an inexpensive CCD black and white module should work for you. A CMOS camera would also work, but is probably higher resolution than you need, and a bit more expensive.
A board mount CCD black and white camera module should cost less than $50 US. Most CCD modules are fairly sensitive to IR, so IR diodes could be used as illuminators in place of visible light. CCD modules run on low current, and require 9VDC or less. That makes portibility less of a problem.
Do a Google search for ccd b w camera module and you should turn up quite a few prospects. A simple search for b w camera module will return a different assortment.