PSPTUBE, it seems like finally this small software works.
this software will allow you:
watch youtube videos on your psp, with wifi conection. no more flv converters, etc. you can watch videos as i f you were on a pc.

ok i deleted the guide. the guide isnt for noobs and its clearly that the people asking for help here are noobs. i dont give support to this app since its not mine, the app worked for me those days when i had a psp. here is the app

http://www.pspmod.com/forums/wireless/20212-psptube-now-you-can-watch-youtube-psp.html

and you can there learn how to do it. you need a custom firmware!!