I initially created TinyBrowser (a file browser for web applications) for my own use, as part of my LunarWeb Content Management System, before deciding to release it under the GPL for the benefit of other users.
I have to say I've been completely blown away by the response I've gotten. I'm getting several emails a day from users, plenty of feedback, bug reports and shows of gratitude - a great massager for the ego!
At first TinyBrowser was exclusively for use with TinyMCE, but I've gone on to add support for FCKeditor (still in experimental stage) and also a stand-alone mode for use in your own web app.
My design philosophy was to make it as functional but easy to use as possible. Standard html form file uploads have always been a bugbear of mine due to their limitations - specifically the inability to upload multiple files and to filter by file type - so that was a primary goal with TinyBrowser. In the end, I utilised a Flash-based upload tool that provides those two requirements along with a nice GUI including stuff like sortable columns and upload progress bars.
I've set up a Google Group for discussion of TinyBrowser (and access to the latest betas).