This works really easy. Just install the blackrain tool on your Mac or Windows machine and connect your IPhone – jailbreak done within 5 mins… Unlock takes annother 5 (open Blacksnow on the Iphone and install the Crack).
So, my 3G is unlocked and ready to be sold (buyer already there)… I’d probably jailbreak my 3GS as well, but with a quick glance through cydia, I could not find an App I’d really need… do you have any suggestions?
Anyway: Thanks,GeoHot 
PS: Good explanation how to jailbreak / unlock your IPhone: http://www.iclarified.com/entry/index.php?enid=5885
Okay, now more examples and more details:
SBSettings: saves you a lot of time regarding switching on/off phone mode / WLAN / 3G
Orbit: Exposé for iPhone – very cool if yu have more than 5 screens full of apps (not free)
WinterBoard: if you love eyecandy and want a new look for your iPhone
MxTube: download movies from youtube instead of always waiting for delays while playing ;-/
Ja, Sbsettings sind cool, allerdings hab ich sonst nichts installiert. Ich denke über das winterboard nach, aber ich bin auch so mit der optik zufrieden.
Eher noch so was, dass die Termine im Lockscreen anzeigt.