There are a number of cool apps for a jailbroken phone that you cannot get via the app store, although most of them are not working on the 2.0.x phones yet… waiting….
However, even just for these 3 apps/functions, its worth it.
1) Record video. The quality is not that great, normally around 15 fps, but good enough to have video that is enjoyable. Why Apple did not release this with the OS, I’m not sure, but I have a bet that they will partner up with a chosen company and put it on the app store. Here are two reasons for this guess; First, there are levels of the OS you need to get to to record video well, second, EVERYONE will buy this app. At 30%, Apple will make pretty good money on it.
2) SSH/Telnet/UNIX tools. Really, if you have to ask, then you do not need this.
3) Changing of default sounds and graphics. Although you can COMPLETELY change the look and feel of the iphone, the big value for me is changing the alarm sounds. FULLY! That weak sound is useless for a sleeper like me. I need something with some punch! I use ‘FinalFantasy_Vicotry’! Wakes me up every time.
Now if you are into playing with redesigning the look and feel of your iphone, check out this site. Here are a few samples.