[dpeterson3]

I didn't get to use any sensors with the FRC bot last year (granted I tried, but my ideas were shot down). With other bots however,
Lego's light sensors (old RCX style) are very good for sensing different colors
Light encoders are very cheap and easy to build. (1 cds cell, 1 LED, and one old cereal box )
a compas would be very useful to tell the bot which alliance it is on
switches alone are very powerful for sensing a barrier or limit
pots are good for telling angles

I've never tried this one, but it makes sense. I have seen designes for using cheap mic cartagres as touch sensors. When the robot 'hears' the bumper move, it senses it hit something/