blog.us.playstation.com/2008/04/07/psp-firmware-v395-coming-soon/

Just a quick update, we’ll be making PSP firmware update 3.95 available shortly. The update includes the following:

While playing PSone games on your PSP, you can now customize how the buttons are assigned by going to [Controller Settings] > [Assign Buttons] and select [Custom]. 

You can now quit Remote Play and choose to turn off your PS3 or leave it on after quitting. This is useful if you are performing a download and want to quit Remote Play, but still want your download to continue on the PS3. Select [Quit and Turn Off the PS3 System] or [Quit Without Turning Off the PS3 System] from [Quit Remote Play] when you press the HOME button on the PSP system.

Nothing really huge, but some nice additions to make PS1 games and Remote Play a bit easier to use/play on the PSP. 

A lot of people expect a lot from firmware 4.0. Then again there might never be a 4.0 but I'm pretty curious about whether or not they're going to do something special with it soon enough.

Anyway I don't have a PS3 so this update doesn't affect me. Heck I didn't even update yet.

For 4.0, I'd guess we'll finally see the PSP get its own PS Store, which Sony mentioned was in the works at GDC, so there's no better time to put it out.