"Indeed there is a power in Rivendell to withstand the might of Mordor, for a while: and elsewhere other powers still dwell. There is power, too, of another kind in the Shire. But all such places will soon become islands under siege, if things go on as they are going. The Dark Lord is putting forth all his strength." - Gandalf "Fellowship"
They are boxed in by the "Bounders"/Men of Westernesse, Tom Bombadil and Cirdan ...so possibly this, or, maybe Gandalf refers to himself since he bears the ring of Narya?
I had originally been as curious as to whether there were references in Tolkien's other works suggesting an alternative meaning besides Hobbits, being bothered by the "Sharkey" elements described in my comments below. The arguments in favor of a Hobbits interpretation are quite sound, however, and later passages in this same chapter actually further reinforce a Hobbits interpretation. Eg., when Glorfindel [ at least I think it's Glorfindel ] lists powers capable of opposing or withstanding Mordor; Lorien, Cirdan and Rivendell are mentioned. The "Power of another kind" definitely suggests a power that is known by Gandalf alone and as is mentioned below, he is well aware of the Hobbits' unique attributes.