A Flash Player for the PSP has been released.

PSPHacks.net and 71M, in cooperation with RK Digital.net, Heavy.com and Newgrounds.com is proud to present the PSP Flash Player!
The current version supports most action script through version 7 and runs on 1.5 only. We are currently testing for 2.x PSPs and will announce when it is working on 2.x firmwares. If someone gets it working, be sure to let us know.
Source will be released in a couple of days once we get it all cleaned up.