Zeroshell is a Linux based distribution dedicated to the implementation of Router and Firewall Appliances completely administrable via the web interface.
Zeroshell is available for x86/x86-64 platforms and ARM-based devices such as Raspberry Pi. MajorGeeks mirrors are the Install/Live CD x86/x86_64 version. Visit the author link above to download for Raspberry PI, although that distro isn't updated frequently.
Load Balancing and Failover of Multiple Internet Connections
VPN Site to Site and VPN Host to Site
Captive Portal Access for Internet Hotspot
Firewall Rules using Deep Packet Inspection (Layer 7 Filters and nDPI)
Quality of Services and Traffic Shaping using Deep Packet Inspection