Shimano Octalink crank compatibility Are Shimano Octalink crank arms interchangeable between different model chainsets?

If so, which will fit my Deore FC-M510 hollowform chainset?
On a traditional square taper or Octalink (V1/V2) or ISIS system, the two crank arms never touch -- you're free to mix and match the two crank arms so long as they are both compatible with the bottom bracket's standard (e.g. you could have a Shimano right crank arm and a SRAM left crank arm on a standard square taper, if both crank arms are square taper). Note that Octalink V1 is not compatible with V2 and vice versa.

Typically though, you don't just get one crank arm. If you have one thats worn off or damaged some how or whatever, your best bet is to either buy a whole new crankset, or go to a bike shop and see if they have a spare arm in their parts bin.

[Obviously, you need to choose a crankset compatible with your frame/rest of setup to get the correct chainline and teeth counts and stuff, but that's not part of the question]