Step 1. Make sure the SOCKS tunnel on your work computer allows LAN connections so your iPhone/iPod Touch can connect to it.

ssh -N -g -D 1080 user@domain.com

Step 2. Create a text file and insert the following code:

function FindProxyForURL(url, host)
{ 
     return "SOCKS 192.168.xx.xx:yyyy";
}

Replace the x's with your IP and the y's with the port you used after the -D in your SSH command

Step 3. Save the text file as a Proxy Auto-Config (PAC) file to a web accessible place with a .pac extension.

If you're reading this chances are you know how to serve a file over HTTP on your work LAN, so I won't delve into that.

Step 4. Finally, on your iPhone/iPod Touch, go to Settings>Wifi and click the blue arrow to the right of your work network. Scroll to the bottom, click Auto and type in the address to your PAC file (e.g. http://192.168.xx.xx/mysupersecretproxy.pac).