PSP3D is reporting that the PSP-OSS homebrew is nearly complete.

Here is a list of the features:

Working Features:
-MP3 playback
-OGG playback
-PNG viewing (pictures (only 480×272))
-EBOOT Loading from within PSP-OSS
-UMD Loading from within PSP-OSS
-Fully skinnable (reboots the OSS to change skins)
-Wallpapers changable while in the OSS
-NEW: File Browser

Coming Soon:
-JPEG viewer
-Text viewer
-Many more features…

Compatability:
At the moment, PSP-OSS should only work for firmware 1.5.
They doubt >= 2.0 support will be in their first BETA. Maybe not even until kernal mode is ready in 2.0 and higher.

Release Date:
Early version available for the public hopefully available by Christmas.

You can download a video of it in use here.

This is something I am eagerly anticipating as it looks great. Right now I use PSPWindows which is ok, but not nearly what I am looking for. I will be downloading this as soon as it is released and will talk about my experiences in forums when I do.