You can now download the official iPhone App for Wikipedia from the app store (iTunes link) for free onto your iPhone. This is the first official iphone app for wikipedia and is published by the WikiMedia foundation. As ReadWriteWeb points out this app is not very different from the mobile version of the wikipedia.
One interesting feature I noticed is the history tab, which displays all the recent topics you visited. But its just an iFramed version of the mobile site so its kinda slow and laggy. You need an active internet connection to use it and just not support offline downloads. There are many 3rd party apps in the app store which offer such features and this official app looks incomplete. But its great to see Jimmy Wales & Co building this app and getting it out out us.We look forward to more updates to this application. For now just head to the app store and give it a go