Here's how you can install the PPSSPP PSP emulator in Ubuntu 13.04. Please note that there are different commands for the 32-bit and 64-bit versions of Ubuntu 13.04.
1. Open a terminal window.
2. Type in the following commands then hit Enter after each.
wget -O ppsspp32.deb http://goo.gl/trQ2dR
sudo dpkg -i ppsspp32.deb
sudo apt-get -f install;rm ppsspp32.deb
wget -O ppsspp64.deb http://goo.gl/ndhkJP
sudo dpkg -i ppsspp64.deb
sudo apt-get -f install;rm ppsspp64.deb
PPSSPP is a PSP emulator written in C++, and translates PSP CPU instructions directly into optimized x86, x64 and ARM machine code, using JIT recompilers (dynarecs). PPSSPP is an open source project, licensed under the GPL. PPSSPP can run your PSP games on your PC in full HD resolution.More at Noobs Lab
Additional resources for PPSSPP PSP Emulator