Youve got to download
dolphin HD...best browser Ive tried for Android.
Advanced task manager is also a must. It comes with a "PUSH TO END ALL" widget that ends all tasks.
Handcent SMS is way better then the stock text messaging app.
Also, if your like me and have cool things popping into your head all day, be it story ideas, game dynamics, or just quotes from characters...you have to download
SPRINGPAD...its basically just like a notebook, for tiny notes, except you can make lists, attach pictures, anything...and it all syncs online so you can get everything from your computer.
Anycut (free) or
bettercut (paid) is a great app that lets you put shortcuts to ANYTHING.
PANDORA IS AWESOME!!
Robo Defense is one of the best android games out there.
Root Explorer and
ASTRO are the best file browsers...but you need ROOT obviously for root explorer.
If you get root,
set CPU is awesome for overclocking your phone CPU. also
Wireless Tether lets you tether your phones 3G connection to a wifi hotspot your computer can use.
Again if you have root,
Terminal emulator, and
autostart are two applications. If your a tech head like me, you probbably want to write scripts and such and run them to do cool things...Autostart lets you run scripts at startup.