Recip saw blades have a fair amount of flex in them, but there's only so much they can take before bending. Avoid using your hands to straighten them as you can burn or cut yourself, and pliers can leave a kink in a blade at the spot where you try to re-bend it.
To straighten, lay the blade flat on a scrap 2x4 with the bend arching up. Strike the blade a few times with a hammer to flatten out the bend. Be careful not to hit the teeth on the blade, as that will damage them. Check out the video above for more.
Unbend a Sawzall or Jigsaw Blade [John Heisz (YouTube)]