I also suffer from this same problem. I shouldn't have to get an App to do this. The phone should do it. Blackberry has been doing this for years. Also I don't want to have to ask my customers to put conference/bridge info in a specific format. The apple engineers are heralded as the best, and they should be able to recognize most popular formats such as:
(800)555-1234 / 123456#
(800)555-1234 passcode 123456#
(800)555-1234,,123456#
Moreso, if the phone number happens to be in the notes field like this:
Conference: (800)555-1234
Passcode: 123456#
I would also expect the iPhone to be smart enough to recognize this and prompt me as well to dial into the bridge line properly.
I have sent a request to Apple about this through this form
http://www.apple.com/feedback/iphone.html and I hope others here will do the same. The more people that ask for a feature, the more likely it will get implemented.