Here are the best and most usefull n73 free applications,
Video Player:
DivX Player. This playes is the best one as it playes AVI format and delivers extreme quality and clarity.
Get it from here . http://gallery.mobile9.com/f/68106/
Blogging and Photos uploading:
For Blogging and photos uploading i recommend Shozu. It is an excellent application for blogging and publishing photos to other sites like picasa and fliker.
Get it from here. http://www.shozu.com/portal/index.do
Chatting :
For N73 it slik only. I provides a pop up alert when anyone pings you this is great and speed is also good bcoz of light weight UI.
Get it from here.. http://www.lonelycatgames.com/?app=slick
Reading :
Use Mobi pocket for reading book. you can get tons of free books from project gutenberg.
Get it from here: http://www.mobipocket.com/en/DownloadSoft/default.asp?Language=EN