Resco Explorer is a file manager for Windows Mobile that I use as alternative for native file manager. Unlike Windows Explorer, that supports only basic functions, Resco Explorer has dozens of useful features. There are such features as registry-manager that makes editing of registry possible, ftp-tool, zip de-compressor, network browser, encryption-tool, viewer for text and graphic, today plugin with system information + quick launch toolbar and so on.
But not only the features played a big role for me, but also design and it is really good.
There is only one disadvantage for me, it is the price of $24.95.