Despite harsh criticism from AT&T, which claims Google is breaking federal telecommunications laws by blocking premium phone numbers (such as phone sex lines), Google Voice is finally back in action on the iPhone.  Rather than try to wade through the App Store submissions process again and likely be rejected, Google this time opted for a web app, accessible via the iPhone's browser.

The new HTML5 app is tailor-fit for the iPhone and Palm smartphones (webOS), though it will work on any HTML5-ready phone.  Texting is easy, but calling has been partially crippled. 

Basically, to call you still have to place a call to a random Google number.  This means that downsides are that your call history will be filled with random numbers and you will still pay for the minutes.  The upsides, though, are that you can use the service as a means to mask or screen calls on your mobile, and you can get international calls at much lower rates.

To try the new service out, go to voice.google.com (you will need to make a Google Voice account before you can use the site).  The page might not be up yet, but refresh until it is.

For those thinking that web apps may be a new way to skirt Apple's restrictions, it's important to keep in mind that its much harder to develop a full-featured web app for the iPhone versus a dedicated app, which can leverage Apple's APIs.  Also, Apple did likely give Google the okay on the web app, so there's no telling whether Apple would try to block future rebel web apps.  Nonetheless, some see promise in this path.