Try BBNotePad. It is free.
BBNotePad is a plain text editor that allows you to write full-length documents or even code wherever you might be. BBNotePad sports three text sizes and it saves files as .txt files that can be opened directly on any computer, saving to either your BlackBerry's internal memory or on your removable flash card. It's very useful for sending notes and memos over Bluetooth to other handheld devices.
For your computer, you'd need a MicroSD card reader, or a bluetooth transceiver if you wanted to transmit the text file wirelessly.