I think this has already been proposed before, the reason I'm writing this is that I realized that half of the work to have wikipedia on a psp has already been done:
there are several version of Wikipedia already available in the Encyclopodia Ebook format (a spec designed to port wikipedia on small, embedded systems). A reader that support the format is all that's missing to have wikipedia on every psp.
If you are interested the specification for the format are here: encyclopodia sourceforge net/ ebookformat html
some working code (for ipod) is here:
encyclopodia sourceforge net/ en/ index html
and some wikipedia editions are here:
encyclopodia sourceforge net/ en/ library html
(links broken to circumvent the spam filter, sorry
I really hope you like this idea, it would basically turn your psp in The Hitchhiker's Guide to the Galaxy.
If any hb developer is looking for a good idea to work on... well this is my humble proposal :)