GHSkinz, a company that specifically makes skins for Guitar Hero and Rock Band instruments is now opening up a line of skins for handheld systems. The PSP is included, but unfortunately has the most ridiculously expensive ones at $10.95 a pop. That's more than double the price that their Nintendo DS and iPod Touch lines go for.
That's not to say that their products are not any good; the designs are quite beautiful -- just have a look. It just makes us scratch our heads as to why the PSP gets screwed over with such a large bill. Anyway, that's expensive in our minds but ultimately that's up to you if you're willing to pay the price.