No, there is not. It is currently not possible to have Ubuntu or any other operating system on the PS3. Sony killed the 'Other OS' feature. There is an expception: the 'Other OS' feature is disabled by firmware version 3.21 but still runs on older consoles that have firmware 3.15 or lower. This would mean though that there is no access possible to PSN or any other web feature since this will prompt for a (mandatory) update.

Any other methods installing another OS would be illegal in most countries (if not all). And even if it is not illegal... circumvent Sony's PlayStation 3 security algorithms or run unauthorized software on your PS3 and Sony will sever your access to its PlayStation Network for good. It involves hacking your PS3 but AU is not going to provide you with the instructions to do that.