PSP Firmware 6.00 Update Filename: PSP_600_FW_UPDATE.RARSize: 27.41MBDownloads: 50,176
Description:
Sony's official 6.00 firmware update for the PlayStation Portable.

5.50 Firmware Update Filename: PSP_550_FW_UPDATE.RARSize: 26.26MBDownloads: 1,292,748
Description:
Sony's official 5.50 firmware update for the PlayStation Portable.

• [Information Board] has been added as a feature under [PlayStation®Network]. You can view the latest news from PlayStation®Network.
• Support for a Web security service provided by Trend Micro™ has been added to [Internet Browser].
• An icon for [Internet Search] has been added to the menu bar in [Internet Browser].
• In the options menu for a game under [Game], you can now perform an Internet search using the name of the game as the search keyword.
• You can now view one more folder level under [Photo], [Music] and [Video].

5.00 Firmware Update Filename: PSP_500_FW_UPDATE.RARSize: 25.83MBDownloads: 1,544,462
Description:
Sony's official 5.00 firmware update for the PlayStation Portable.

• The [PlayStation® Network] category has been added, and [PlayStation® Store] is now available under this category.
• PlayStation® format software can now be output in interlace format on a connected device.
• PlayStation® format software can now be output in full-screen size on a connected device.
• The sleep timer feature can now be used under [Music].
• The system will automatically change to USB mode when a USB cable is connected.
• The [Original] theme has been redesigned.
• A new full-screen keyboard; press [Select] when the OSK is displayed.

4.05 Firmware Update Filename: PSP_405_FW_UPDATE.RARSize: 24.57MBDownloads: 68,499
Description:
Sony's official 4.05 firmware update for the PlayStation Portable. This update adds new visualizers for music playback.

PSP 3.52 Firmware Update Filename: PSP_352_UPDATE.RARSize: 20.55MBDownloads: 891,235
Description:
Sony's PSP 3.52 Firmware Update. You CANNOT run homebrew or downgrade with this version, not yet anyway. :)