uBiome are offering free kits. They are in the States and you have to pay postage to Europe, but still worth it in my opinion.
Order the single kit at ubiome.com and enter the code Radiolab3 when checking out.
I have no idea how long this offer will last for, and cannot vouch for the quality etc because I have only just ordered. But since I am pretty sure that my gut isn't entirely weed free I thought it would be interesting for $20 plus the postage back, of course.