I have several apps that i use frequently most noteably are the nes, snes, and gba emulators. I also enjoy the ability to open a termal on my phone and run any number of command line applications such as vim, ifconfig, find, grep, etc... But like texrat stated above, the real killer app pf the n900 is the microb web browser. Full web experience, what you see on you desktop is what you see on your phone.