UPDATE*** NO LONGER WORKING!!!
run this program on your pc and configure your network settings in PS3 to use a proxy. Use your computer's IP as the proxy. No need to update to 3.56 Works great (for the time being)!
Logan5's PS3 Proxy tool Dashhacks :: PS3-Hacks :: Logan5 PS3 Proxy Tool
UPDATE: It does work! make sure you have any firewall software or portblock stuff turned off! (it runs well in a virtual machine with bridged networking.. then you can leave firewall software on host turned on without having to configure exceptions)
rather than using a common dns.. this uses your same WAN ip as your real ps3. isn't that maybe safer? correct me if I am wrong?
UPDATE2: in light of recent $ONY legal developments (suing everyone!) I feel it extremely important to establish the facts: that I am neither the author of this software, nor do I recommend or condone its use. I post this link merely for educational purposes and am not held liable or responsible for your choice to download and/or run this application.
UPDATE3: Found alternate method for linux. not sure if it is up to date... all three methods can be found here. How to Access PSN Bypassing PS3 Firmware 3.21 Upgrade for OtherOS » My Digital Life