EDIT: These are now expired.
There are only 10,000 free Weber BBQ seasonings available on Facebook, but I haven't seen many other sites post this, so tons of Hiffers should be able to snag a sample. Now when I forget I have burgers on the grill, their charred remains will at least be seasoned!
Of course right as I published this, their signup form started spitting out errors when you hit submit. You may have to try back in a few minutes/hours.