Software that i need?

you can always check www.versiontracker.com or www.macupdate.com for cool little apps. I particularly like OnyX, allows for some cool modifications, as well as running the cron jobs that are supposed to be done in the middle of night, when my pb is sleeping

Candybar is great for changing your icons

These aren't "necessary," per se, but I enjoy the following software:

Proteus (for instant messaging -- compatible with AIM, etc.)
Konfabulator (little widget things ... you pick the ones you want)
Stattoo (time, weather, calendars, etc. embedded into your desktop)

www.proteusx.com
www.konfabulator.com
www.panic.com/stattoo

MacStumbler
www.macstubler.com

A nice WiFi utility that lets you find other wireless points nearby. Faster than the Airport menu, and lets you know if there is encryption on the network.

Macjanitor
Adium
Transmit

There'a been quite a few threads on this so try doing a search to get a more extensive list. Here's a good thread to get you started.

Off the top of my head, here are the shareware/freeware apps I like:

Quicksilver - application launcher
VLC - for all your media content needs
ONYX - maintenance
Synergy - itunes controller via hotkeys and menu bar
Omni Graffle - great diargramming tool
Backlight - superflous visual effects to impress people!
Little Snitch - to keeps tabs on apps phoning home
WinSwitch - saves valuable menu bar space for fast user switching
Sidetrack - gives full functionality to your trackpad
SuperDuper - for backups

Sorry couldnt be bothered posting links, search www.macupdate.com for all the apps. 🙂