Actually, as the versioning indicates, since the last reported PSP firmware release on UMD Talk, there have now been two small updates.
PSP firmware 3.51, available at the end of June and briefly reported on in news of the PSP Slim apparently running 3.6 firmware, brought a small security patch while 3.52 expands support for PLAYSTATION®Network titles.
As usual, the update can be grabbed from SystemUpdate.
