So I've got a Nexus One (in Off-topic)

A Google Nexus One (HTC) and I can get on the internet from 11th of October onwards.

What apps are good to get, which ones are a must have?
Please divide your recommendations based on free or paid :)

I could be wrong but I don't think you are going to get much help from anyone located in the states. That phone is not currently being sold her anymore.

Still, using android OS so I think there could be plenty of people who use this OS instead of an iPhoney or winblows based OS on their phone :)

Google Maps for Android comes with a very good satnav that is free.

I also use a couple of camera apps (I've a Sony Ericsson X10 which has an excellent camera). The apps are Camera 360 (free version) and Vignette (the demo version which is almost fully functional). They give you some excellent effects, especially the ones that mess with colour and various focus effects.

Apart from that there are some must haves:

Astro file manager. I'm not sure about HTC phones, but mine doesn't give you easy access to files. Astro lets you use the file system exactly as you would on a computer. Very useful.

Advanced Task Killer Free. Apps open by themselves or don't close down when you think they are in Android. This can be set to close those you don't want running in the background and leave alone the ones you do. It will do it automatically for you, or you can go in and do it manually. Helps save running memory and battery.

antivirus: there are two, one called antivirus and one called Dr Web. Both worth using.

Battery Indicator - puts an icon at the top of your page to show you battery level by number rather than a picture icon

Rockplayer - a video player that lets you view all kinds of video types. Very smooth. Very handy for watching films or tv that you might load onto your phone.

So far I've got Whatsapp, bit like text messaging but free :)
I've got Shazam, perhaps overrated but it's free :)