Jailbreaking and unlocking the iPhone has never been easier. In the case that you want to upgrade to the newest firmware immediately when the SDK applications become available then a full restore will set your phone back to factory settings and you will be clear for the upgrade. Here is the site to download the JB/unlock software. The entire process takes under 5 minutes.
http://www.ziphone.org/
Once you're jailbroken just play around with Installer and try out some applications you think you might like.