According to the apple website iOS 4 should support wireless app distribution. I have been unable to find any documentation at all on how to host your applications for users to download them over wifi/3g.
We are currently enrolled in the standard iphone dev program, as we don't have over 500 employees. Is this limited feature limited to the enterprise program only?
iPhone OS 4 enables enterprises to securely host and wirelessly distribute in-house apps to employees over Wi-Fi and 3G. Apps can be updated without requiring users to connect to their computers.
Found a guide on how to get wireless app distribution working. You do not need to be part of the enterprise program for this to work.
http://jeffreysambells.com/posts/2010/06/22/ios-wireless-app-distribution/
If you don't have an entreprise account. You won't have the unlimited or very large pool of devices you can add to your account distribution profiles. BUT, even with normal accounts you can definitely create an Ad Hoc distribution profile (limited to 100 devices) and use the Xcode 3.2.3 "Build and archive" + "Share app / Distribute for entreprise" feature. This will create a .IPA app bundle that already contains the distribution profile. All you need to do is create a web page on some server containing a link with some special scheme.
For instance:
<a href="itms-services://?action=download-manifest&url=http://www.myserver.com/ota/myapp/appname.plist">Install My App over the air</a>
More info directly from Apple at: http://developer.apple.com/iphone/prerelease/library/featuredarticles/FA_Wireless_Enterprise_App_Distribution/Introduction/Introduction.html
Apple Developer account required.
The official documentation is no longer tagged as pre-release (and no longer requires a dev login):