The lens on my Nikon Coolpix L20 got stuck, 1/3 of the way.

If it’s been dropped or suffered some other accident it could be that the lens barrels have been distorted or damaged, otherwise the most likely cause is dirt between the barrel sections. We have a few hints for removing it on the Restart Wiki. If those don’t work, look for a disassembly guide or video for you model (or the nearest you can find). If you remove the lens you can actuate the zoom motor with a 3V battery and possibly move it past the sticking point, hopefully freeing the blockage. (See Disassembling Canon PowerShot SX200 IS)