What is the best free VPN service?

Not sure what you mean by decent but here are a couple of articles from MakeUseOf that review free VPNs.

http://www.makeuseof.com/tag/7-completely-free-vpn-services-...

http://www.makeuseof.com/tag/5-great-free-vpn-services-compa...

If you are even minimally concerned about privacy, all free VPNs are terrible. Find yourself a good, reputable paid VPN. Lots of folks whose lives depend on keeping their real identities hidden say this list is a good starting point, but ultimately you need to do some research on how these companies log data, if at all, and what their privacy policies contain. You should also take a look at their reputations.

http://torrentfreak.com/vpn-services-that-take-your-anonymit...

tunnelbear.com

Use this cheap vpn, http://www.purevpn.com/ and don't risk the bots, malware and identity theft common to the free vpn's and proxies.

Hola Unblocker or Tunnelbear