Ah, putty is more featureful than I realised. I had a dynamic tunnel set up for port 9000, which I used with Firefox's socks proxy configuration. I did more reading and found the better way. I didn't understand "destination" is relative to the remote machine, so localhost is the remote machine. Source port is what you connect to, so in my case, I put localhost:9999 iuto my browser, and get to 192.168.1.2:80 on the remote machine.
This link is really helpful:
I can even remote desktop to my work pc from home, after remote port forwarding port 3389!