This C. Crane FM Reflect antenna by Sangean is said to be simply the best indoor FM antenna.  It works with any portable or stereo receiver.  It's flexible and can be adjusted for signals with circular polarization.  The antenna is made with the dipole design for maximum gain across the entire FM band.  It is up to 213% more powerful than the standard dipole antenna.  The antenna covers the entire FM band, no drop off at the ends.