Now here’s a way to build some quick publicity (and quickly clear out some old stock). Best Buy will be offering the 8-gigabyte iPhone 3GS for free with a two-year AT&T contract later today (December 10), Engadget reports.

The deal, which will only last one day, certainly isn’t meant for smartphone power users. The iPhone 3GS is one generation behind the iPhone 4. And with 8-gigabytes of storage on board, it’s not going to be the best option for storing your music collection and having room left over for taking photos and videos. But still — it’s a free iPhone!

The deal follows Radio Shack’s offer of the first iPhone sale in history — $50 off the 16GB and 32GB iPhone 4 (and a mere $49 for the 8GB iPhone 3GS). Radio Shack’s deal ends December 11.

There’s a lot we can read into Best Buy’s offer. Sure, the retailer could just be looking to spice up sales leading up to the holidays. It could also potentially make a killing off accessories from customers overjoyed with their shiny free iPhone. But it also seems clear that Best Buy is clearing out its stock for something, and that could very well be the Verizon iPhone.