Difficult to know which category to put this, so here will do for now until a mod decides for the better.
Basically your next 10 sales on playtrade will be commision free.
Pretty good as I just sold 3 things for £20 each and got a rebate of almost £10. The playtrade fees are high but you get better prices for your items and they cost nothing to list.
As confirmed by Jayok, the items you list have to be sold before the end of the promotion (31st Jan 2009) in order to be eligible.