If you need to web browse securely on an untrusted network or you're behind an overly restrictive web filter, use an SSH tunnel.
ssh -fND localhost:8080 me@my_remote_host.com
That brings up the tunnel. Any traffic to port 8080 on your local machine will go down a secure SSH tunnel to your remote host. To bring down the tunnel, just kill the SSH process.
To get Firefox to use the tunnel, go to Edit → Preferences → Advanced → Network → Settings. Select Manual proxy configuration. Set Socks host to 'localhost' and the PORT to '8080'.
You may also want to send your domain name lookups over the tunnel. Enter 'about:config' in the Firefox URL field. Find 'network.proxy.socks_remote_dns' and toggle it to 'true'.