What do you mean by plugins? You mean homebrew?
Plugins are like extentions to game and the main menu, which do things like overclock, cheat, and add other features.
If you're looking for homebrew, here's a list of some of my favourites:
1. iRshell / iR Shell - All-in-one connectivty center, homebrew launcher, media player, file manager, and UMD launcher. You can even listen to music while playing UMD's or homebrew!
2. Attack of the mutants - Fun 2D space shooter
3. PSP Quake - A Quake port for the PSP
4. KETM - kill every thing that moves - A cool 3D air fighing game
5. 48 hour pong - A pong game that's first release was coded in 48 hours; features score submission to an online database
6. Devhook - Firmware and UMD/ISO emulator; supports up to firmware 3.03 currently
7. Links2 - A port of the web browser 'links2' to the PSP. Faster than the offical browser, but doesn't always show the page properly.
8. 'SmashGPSP' - A clone of the N64 game, Super Smash brothers
9. PSPRadio - Wi-fi music player that streams from the shoutcast servers
10. Daedalus - N64 emulator, not full speed though it's very good
11. GPSP -GBA emulator, almost always full speed
12. Nem's hello world - The first ever PSP homebrew. Cool to have lying around!
13. PSP soldier - online 2D shooter
14. Frogger - Frogger clone for the PSP
15. X-flash - Awesome flash modification tool; runs only on 1.50, 2.71 SE, 3.02 OE or 3.03 OE
16. Squarez - Addictive endurance game
17. PSPlayerMT - Movie player supporting AVI, MPG, etc
18. AFKIM - IM for MSN, AIM, ICQ
19. Install-o-tron - Automatic homebrew downloader and installer
20. PSP Revolution - Clone of the infamous, addictive 'Dance, Dance Revolution'
21. Jump Gunnar Jump - A cheesy but fun jump n' shoot game
22. PSPool - A Pool game for the PSP (By pool I mean the ball game)
23. PSP Filer - A cool file manager that supports copying to/from Flash and RAM
24. Lua Player - Run Lua scripts
25. PSP PDA - All-in-one utility including a text editor, image viewer etc, for the PSP
If you see any you like, go to
this site and search for it. If you get no results, try changing the wording or Googling it.
Of course, you've also got PS1 games. If you want to know more, just post so and I'll fill you in!