Robert A. and Percival have just released the second homebrew game for 2.70-2.80 firmwares (technically compatible with all firmwares 2.0-2.80).
TIFF Pong, as it's called, is a simple homebrew Pong game, which utilizes the TIFF exploit in conjunction with the just-released 2.70-2.80 SDK developed by Noobz.
Many remember the time when the GTA exploit was at the stage that the current TIFF exploit is now: eLoader-less.
It's amazing how fast the PSP hombrewing community has been blazing through firmwares with exploit after exploit. TIFF Pong brings back tears of nostalgia from the memories of the past (for those who had a PSP in the days of yesteryear). Nothing's better than some retro-Pong gaming on the go!
Note: If you're having trouble getting this to work, try highlighting the PONG folder in the PHOTO menu, then press Start to start a slideshow. This seems to be the most reliable method for running it.