Here are some legal and legit sites with free stuff.
flash games – http://www.psponme.com
game demos – http://www.pspdemocenter.com
videos – http://www.guba.com/home_free
videos – http://psp.connect.com
For music I would suggest you try Streamripper which works with Winamp and Shoutcast. You pick a station on Shoutcast and it plays in Winamp. Then Streamripper will basically record the music into MP3s that you can put on your PSP.

here is info blog about movie download sites (comments, comparison, links…) including psphttp://moviedownloadinfo.blogspot.com/