the only way to uninstall apps like skype, cityid, etc is to root your phone.
that said, they really shouldn't be popping up if you don't open/use them. you could try checking the settings for the offending app and make sure its not set to sync, etc.
note: if your talking just about the apps showing up in "running apps", these won't necessarily cause problems, Android is NOT like windows, just because the app is there doesn't mean its hurting anything or using resources. Besides sitting there annoying you in the list