Are there any puns in stave 3 of A Christmas Carol?

Yes, here is an example of a pun in stave 3. While Scrooge is with the Ghost of Christmas Present, the ghost takes takes him to the home of his poor clerk, Bob, and his clerk's family, the Cratchits. The spirit smiles when they reach the house, and he sprinkles his special torch on the family's dwelling. Just then, the narrator says:

Think of that! Bob had but fifteen "Bob" a-week himself; he pocketed on Saturdays but fifteen copies of his Christian name; and yet the Ghost of Christmas Present blessed his four-roomed house!

Thus, the narrator (ironically) marvels that this lowly person who makes such a little amount of money is lucky enough to be blessed by the spirit. Bob is Mr. Cratchit's first name, but a bob is also another name for a shilling. So, we learn that Bob makes fifteen shillings a week. The sentence includes a pun made of these two words. A pun is a comedic device that exploits a word with two different meanings (like this one: Bob is a name and bob is another name for a shilling) or two words that sound similar and have very different meanings.