If you use Cisco WebEx to host or participate in online meetings, Cisco announced at Macworld Expo its new WebEx Meeting Center app that will allow you to attend a WebEx meeting on your iPhone. You can view the WebEx conference slides or the shared screen using the iPhone app at the same time that you participate in the audio portion of the meeting using the iPhone's phone. The app also allows you to see who else is in the meeting, chat with other participants and get details on the meeting in progress. The conference host needs to be using the latest version of the WebEx software for this to work, but there is no addiitonal charge associated with a person participating by iPhone.
You join a meeting from an iPhone either by clicking on a link in an e-mailed invitation or by choosing a meeting listed within the app. WebEx will then call your iPhone. You can find out more details in this article on eWeek.com and this article in PC World. And Cisco itself has a nice, short video on its website that shows off the features as well as a list of FAQs and this press release.
[UPDATE on 3/12/09: Here is a nice review of WebEx on the iPhone by iPhoneCT]
Click this link to download the free WebEx app using iTunes: