Niederwald Denkmal
If you want to explore Rudesheim for anything beyond an hour, park in the hills above in small lots within the woods, and walk in.  Rudesheim has delightful narrow streets and wonderful little shops.  But remember, it is still a tourist trap!  Link to Rudesheim homepage.
Above Rudesheim is a castle devoted to wine making, Johannesberg.  While not the classic fortress along the Rhein, it is worth the visit, if anything to see the picture perfect roses along the castle's west wall.  When you first examine them, you would claim that they must be silk... but they are very real.
Across the Rhein from the denkmal is the small town of Bingen.  On a small hillock above the town is Burg Klopp, which was once a Roman fort.  On the right, the same castle during the winter of 1977-78.
Despite its tourist trap status, Rudesheim is still worth a visit.  It is simply enjoyable to just walk the back streets and visit the small shops, some so hidden away that one wonders how they even do any business.
A rose rarely looks more perfect than this!