We currently use th LM2574-5.0 just for this reason. Our 5V line require around 200mA-300mA which when run through a linear regulator I could probably heat my house since our source voltage is 24VAC which comes up to around 30-35VDC. The regulator works quite nice and is pretty cheap. I've run it up to about 350mA-400mA and it does get warm to the touch but not hot by any means.