100% Free VPN services for accessing geographically restricted content

All geographically restricted web-sites and country-based restriction relies on an IP address. Blocks of IP addresses are issued and assigned to a specific country in bulk. When an IP address is translated to be located in an unsupported country, the web-site blocks access of a user. Thus in order to overcome regional restriction you need to have an IP address belonging to a supported country (primarily the United States or the U.K.).

100% Free VPN services for accessing geographically restricted content

Hotspot Shield (Windows, Mac) allows you to get a U.S. IP address for free. When you browse Internet using Hotspot Shield, you do it with a VPN IP address (in this case you can pretend to be located in the U.S.)
SecurityKISS Tunnel (Windows) allows you to get a U.S. and IP address for free. The free version is slower and allows you to use 300 Mb per day only. Paid plans allow you to browse faster, offer more traffic, support more countries and platforms.

Note that usually free VPNs (at least the most popular ones) do not allow you to make purchases in the U.S. shops. Transactions from clients using IP addresses from such VPN are usually rejected.

See also:
How to access BBC iPlayer, Hulu, Fancast, Pandora, any other region-restricted sites