It's been a long time coming, but internet tunneling for PSP seems to finally be in full-swing. With Xlink Kai, and a compatible Wi-Fi adapter, you'll be able to play Ad-Hoc games, like Monster Hunter, online. Watch Impress was able to squeeze in 2500 people into a Monster Hunter Portable 2nd game room. All that's needed is: an Xlink Kai account (which is currently free) and a compatible Wi-Fi adapter, such as the PCI Gamering XII, which includes the appropriate drivers.
When booting up a game in Ad-Hoc mode, it will make other Xlink Kai users appear as if they're in the same room as you. With Xlink, so many of the PSP multiplayer games that fans have been collecting won't feel so lonely anymore.