Congratulations . And welcome to symbian world.
First hack your phone to install all applications. There are tons of guide. I prefer "drakkarious" method.
You may go to dotsis.com for softwares / applications. Some of must needed apps are. Xplore 1.22(file browser) , divx .90 (play divx videos) , nokia internet radio , cracked ngage , opera 8.65 , opera mini , msdict , emtube( youtube on mobile ! ) , resco viewer ( because default gallery is slow ) , handy taskman ( must must must ) , google maps.
One word of caution. If you're experimenting too much with softwares ( which i think you should at first few weeks ) , phone will obviously become slow and may give some problem . So you should take regular backup of your phone data like contacts etc.