I have several some home made and some I have bought.
The main purchased ones have been Rolly Munro and Proforme. Both work very well, although due to the guard over both of them there is always some degree of clogging and much of this depends on what your turning. Both fair well on green timber. But the Proforme really excells at bulk removal especially on green timber, but it can have attendancy to self feed.
The Munro is a very easy tool to use and if its tend to clog allot its often due to the Guard being closed up to much.This is a common fault with many turners including myself until I realized what I was doing...didnt really pay much attention to the instructions.
There are the Oland type of hollower and these are easily made by the average turner and I confess I have several of these. Easy to make, easy to use, easy to sharpen and low cost as well.