I've been part of a couple 'giveaway' promotions where an organizer gets dozens of product creators to offer 1 product each for free. Everyone involved then promotes the giveaway offer, and the result can be subscribers added to your list.

However much depends on how attractive your product is, and whether you want to pay a surcharge to get your product 'boosted' in the listings. If nothing else, this is good PR but not sure how effective it is as a list building method. Limited results myself.

Hope this helps!