I'm interested in making a game that can be distributed on PSN. Any suggestions?
You have to put money down. Call Sony and ask them about it. They'll tell you how to hook yourself up with the official developer's kit. It will cost money. But of course, you'll make that money in the back end. So the question really is, how confident are you that you can make something that will end up on PSN for sale?
Here is an interesting article on becoming a developer of the "mini" titles that have recently come onto PSN. http://www.pspminis.com/2068/interview-futurlab-on-how-to-become-a-licensed-psp-mini-developer/
In terms of initial cost, you no longer need to purchase a full reference kit (~$10k) and can get away with a reference tool costing $2000 with much of the functionality.
As mentioned above, getting a real devkit and being setup as a licensed studio can take quite a bit of cash. A better bet might be to learn Unity since Unity3 (which is supposed to be out Real Soon Now) will support PS3. That said, Unity Pro is still not cheap, though they haven't said if the free version will support targeting the PS3 last I looked.