Not specifically a hallowe'en ditty but I've heard this Valiente poem sung and it worked rather well out in the woods at night, though I don't have a tune for it:

THE WITCHES' BALLAD

Oh, I have been beyond the town, where nightshade black and mandrake grow,
And I have been and I have seen what righteous folk would fear to know!

For I have heard, at still midnight, upon the hilltop far, forlorn,
With note that echoed through the dark, the winding of the heathe horn.

And I have seen the fire aglow and glinting from the magic sword,
And with the inner eye beheld The Horned One, the Sabbat's lord.

We drank the wine, and broke the bread, and ate it in the Old One's name.
We linked our hands to make the ring, and laughed and leaped the Sabbat game.

Oh, little do the townsfolk reck, when dull they lie within their bed!
Beyond the streets, beneath the stars, a merry round the witches tread!

And round and round the circle spun, until the gates swung wide ajar,
That bar the boundaries of the earth, from faery realms that shine afar.

Oh, I have been and I have seen in magic worlds of Otherwhere.
For all this world may praise or blame, for ban or blessing nought I care.

For I have been beyond the town, where meadowsweet and roses grow,
And there such music did I hear as worldly-righteous never know.