The Sony PSP handheld entertainment system has been out for several years now and has a healthy community of people building applications for it.  Better known as “homebrew,” which some people consider a “gray market” since Sony does not actually support such activities, it is hard to resist when you see some of the fun things it will let you add to the popular gadget!
Here are over 20 homebrew resources, utilities, emulators, and more. Make sure to visit some of the download resource sites to learn how to install these items.

Emulators

ColEm PSP – Reaching way back into video game history, you can now enjoy your favorite ColecoVision games with this emulator.
Daedalus PSP – A Nintendo 64 emulator that even allows you to save your progress at any point in the game.
DGen – An emulator for the Sega Genesis.  Page is in Japanese, but the download is marked and it has an English read me file.
NeoCDPSP – A popular emulator for the old Neo Geo gaming system.
NesterJ – An emulator for the original Nintendo Entertainment System (NES) games.  Please note that the page is in Japanese and this is a translated page, but the download is clearly marked.
Snes9xTYL – Super Nintendo Entertainment System game emulators for the PSP.

Homebrew Resources

Dark-Alex.org – Dark Alex is probably the best known member of the PSP homebrew community, having released numerous custom versions of firmware.
PSP.Brewology.com – Features downloads, pack generators, a wiki, forums and more.
PSP-Hacks.com – Besides homebrew files, they also have saves, backgrounds, extremely active forums and more.
PSP-Homebrew.eu – Features a huge selection of programs for homebrew ready PSPs, including multiple versions where available so you can find the perfect one for the OS version you are running.
PSPSlimHomebrew.com – Site dedicated to the PSP Slim version of the player. Has downloads, reviews and general news applicable to the system.
PSPUpdates.qj.net – Huge repository of PSP homebrew news and downloads.

Music

MP3 Player – Just as the name implies, this is a simple MP3 player for the PSP.
PSP Rhythm – An audio sequencer allows you to mix up to 16 sounds at once. You can also export their completed works as CD-quality wave files.
PSPRadio – Allows you to stream SHOUTcast radio stations via your PSP.
PSPSeq – PSPSeq allows you to compose up to 16 separate channels of music, tweak instruments, play it back, and several other features for music composers out there.

Utilities

AFKIM – The AFKIM (Away From Keyboard Instant Messenger) allows you to use instant messengers like Yahoo, MSN, ICQ and more directly from you PSP.
PSP-PDA – Gives you numerous PDA functions on your PSP such as a music player, image viewer, address book, calendar and more.
PSPoste – Well-known email client that supports IR keyboards and has numerous features.
PSPTube – Allows you to add YouTube to your PSP.
PSPWrite – A text editor that allows you to edit text files of just about any size you choose.