Is the comma before "with" necessary?

Solution 1:

Yes. The sentence is a complex sentence. As described by Erlyn Baack on his site titled Advanced Composition for Non-Native Speakers of English, "A complex sentence has an independent clause joined by one or more dependent clauses. A complex sentence always has a subordinator such as because, since, after, although, or when or a relative pronoun such as that, who, or which."

In this case the word "with" acts as the above mentioned subordinator. It is always proper to separate these dependent clauses with commas.

I've broken this sentence down into its individual clauses to try to demonstrate why this sentence is a complex sentence and why it is necessary to seaperate the two clauses with commas:

Independent Clause: The Oscars may not take place until February 24,
Dependent Clause: but awards season is already in full swing,
Dependent Clause: with the Golden Globes among Hollywood's many red-carpet events."

Solution 2:

The above "clause" analysis is incorrect.

By definition, a clause, whether independent or dependent, must have a subject and a verb. "With the Golden Globes among Hollywood's many red-carpet events" has no verb. Therefore, it is not a clause. It's a phrase. A prepositional phrase. And nonessential. It does not modify "swing," so a comma should be inserted.