Just would to share my expirience how to get connected to wl-500g if you are sitting behind
corporate proxy/firewall which disallowed either direct internet nor
"corp.proxy"->"wl-500g: port 22" connections.

The main steps are:
1. Start ssh daemon on yours wl-500g.
2. Create post-firewall script if one doesn't exist.
3. Change (add) iptables rules to redirect all incoming on port 443 traffic to port 22.
4. Configure your ssh client (I've tested with putty and WinSCP3) with your current proxy authetication settings and instruct to use port 443 instead of port 22.

Remark:
It works for me on wl-500g Deluxe router with Oleg's 1.9.2.7-4 firmware (as usual many thanks to Oleg ).

Now a little bit more details:

Step 1: This is very good described by Oleg - how to get dropbear daemon running. Look here: http://wl500g.dyndns.org/ in section "Ssh and telnet daemons"
Step 2: For creating an empty post-firewall script please follow the procedure described by Oleg in the same document. But don't forget to put as first string following:
Code:
#!/bin/sh
Step 3: As I'm not really professional in network administration things, so I've learn those from alpha5's topic http://wl500g.info/showpost.php?p=8990&postcount=2 (thanks to alpha5 )
Please add following strings to your's post-firewall script:

Code:
iptables -D INPUT -j DROP
iptables -A INPUT -p tcp -m tcp -d 192.168.1.1 --dport 22 -j ACCEPT
iptables -t nat -A PREROUTING -i ppp0 -p tcp --dport 443 -j DNAT --to-destination 192.168.1.1:22
iptables -A INPUT -j DROP
Save it and also don't forget to commit changes to flashfs as following (or in different way as you like):

Code:
flashfs save && flashfs commit && flashfs enable
Reboot yours wl-500g.

Step 4: Depending on yours ssh client set apropriated proxy settings (usual HTTP proxy) like address, port number, username and password. And most important thing: Instruct this client programm use port 443 instead of port 22.

Enjoy.