Really useful post on how to reset / reformat Nokia phones. *#7780# - Restore factory settings and *#7370# - Reformat. Handy dandy.
A bunch of dictionaries for Symbian devices, including Spanish to English. :-)
The podcatcher application for Symbian, the successor of Escarpod.
Open source media player (supports mp3, ogg, and more) for Symbian devices. Great for the E51, much better than the in-built player. Supports skip forward / back... :-)
SSH client for Symbian OS for phones like the Nokia E51 and E52.