Flip flopping means little to me and in fact can show a deliberate thoughtfullness and ability to change ones mind when new evidence comes to bear.

But McCain has changed his vote or stand on the following issues;
torture - gave in to Bush torture bill.
abortion
immigration - for it then against his own bill.
social security
Bush permanent rich tax cuts
gay marriage
campaign finance
off shore drilling
surge troops in Afghanistan
and finally he first voted against a holiday to honor MLK