I recently came across with FireSSH (firefox addon).
It has a great potential. The 0.88 version supports tunneling. I connect to my SSH server through FireSSH with no problems at all.
In the advanced tab, I added 7070:127.0.0.1 (tunneling). When I try to make Firefox connect through proxy (127.0.0.1 7070, socks v5), it says that the proxy is refusing connections, like if there was no proxy.
I'm not sure if it's a bug, or me. But I test my connection (to my ssh server) with PuTTy (with a tunnel), and it works flawlessly.
I honestly didn't know where to ask this, I tried to google it, but it seems it's not that popular (firessh tunneling) and looked around in firefox website/developer website but nothing.