Many companies like to give away free samples to encourage you to try then buy their products. Some may charge you P&P, some will be completely free. I will be updating this page with all the latest offers I can find shortly.
Just for starters whilst I'm setting up the site here's an offer I've just used:
Try 14 days tailor made dry food for your dog for just £1 P&P from Tails.com both my dogs love it!