You CAN acces the internet via a PSP but thats purely as a result of the homebrew scene, with a lot of very talented people making use of "back doors" in the PSP's software.
Sony ARE planning on initiating a PSP online gaming scene, using the wireless capabilities at various wi-fi hotspots and using wireless home internet access.
But details are very thin on the ground at the moment.
It'll be similar to the Nintendo Wi-Fi Connection that'll be started up towards the end of the year for the Nintendo DS, as that system is know to use wi-fi hotspots that are going to be built around the UK, along with a wirelss adaptor you'll be able to buy to plug into your pc to allow a DS to go online.
However, the one thing I'm sure of, is that where the Nintendo connection is generally accepted to be a free service, there are ugly rumours that you may need to pay for the PSP service.
Hope that helps.