What tool do I need to remove my crankset?
 

It is a Shimano Octalink. The bb is splined. TIA.

Road or MTB crank? For any of them you need an 8 mm allen key to remove the fixing bolts.

If the crank is an Ultegra or Dura Ace it will have self extracting bolts so you loosen the fixing bolt a turn or so then it will appear to get tight again. Keep turning the wrench and the bolt will pull the crank off the spindle. You won't need any other tools.

If it's a 105 or MTB crank, you need a Park CWP-7 universal puller or CCP-44 for splined cranks. If you have a puller specific to square taper cranks, Shimano made a steel mushroom-shaped tool TL-FC15 that acts as a plug in the hollow spindle and lets a square taper puller work.

It is a mountain bike, a Rockhopper. Looks like I'll need the Park CCP-44. I already removed the fixing bolt but that is as far as I've got. I'm replacing the BB cartridge.

That will get the crankarms off. In order to remove the BB cartridge, you'll need a Park BBT-22: http://www.parktool.com/product/bott...et-tool-bbt-22 or BBT-32: http://www.parktool.com/product/bott...et-tool-bbt-32 to remove the cartridge itself.

Yep, I missed that. I saw the question about "crankset" and only addressed that part of the job.

Thanks for watching out for me guys.
I figure I might as well buy the tools. The bike shop would charge me to do the work. For what I would pay them I'll buy the tools then have them for next time.

+1. Good tools are a wise investment. I still have some from my bike shop days, nearly 30 years ago.