ssh has a really nifty -D option to implement a SOCKS5 proxy.

Therefore

ssh -D localhost:8080 remote.box

and then setup Firefox to use localhost:8080 as a SOCKS proxy server.

But it gets better; If you are worried that DNS requests will leak onto the local network, it turns out with SOCKS5 all you need to is go to the Firefox about:config page and turn on network.proxy.socks_remote_dns and DNS is tunneled too.