For app store apps press and hold the icon of the app you want to delete, when they start to wiggle, if it has an X in the left top corner, tap it, it will delete the app.
For cydia apps, you can use a program called cydelete, which will put the X on cydia apps while they are wiggling and you can tap it to delete, or you can go into cydia, click on the "manage" tab, select packages, scroll to the app you want removed and select modify, then remove.
If you want to remove the apps that came on the phone...you can do that but you will have to be jailbroken.
Im a new user of iPhone. I've use iPhone 3g, it was a jailbreaking, but now i already updated with 3.1.3.. and not jailbreaking anymore.. when i sync to iTunes, it romoved all old jailbreaking apps, except isilo.. i tried to remove isilo from iTunes and directly in the iPhone but it didn't work, the apps icon still there.
Actually i bought the used iPhone.
This apps is came from the previous owner, it was jailbreaking and threre is a cracked apps in it.
i was changed this iPhone from jailbreakin to official iPhone.
i don't have any apps in my iTunes before. so i can't check or uncheck the apps.
after i updated the firm ware from 3.1 to 3.1.3 and syncing, the all cracked apps was gone, except iSilo.
actually the isilo apps isn't in my iPhone anymore but the icon only.
, for you guys i might looking weird, i am the one who won't use a jailbroking iPhone.. we'll see.. maybe oneday i will really need more powerful iPhone and need to be jailbreak it, because, now i felt i really need a multitasking iPhone, which is hopefully it will be in the new firmware 4.0.. anyway thanks for replying and im sorry about my english