Apple’s iPhone may be packed with features, but enterprising developers this week added two communications-related capabilities the phone was missing: voice-over-IP service and videoconferencing.

Tweaking the iPhone has already become a popular sport, with iPhone blogs like iPhone Hacks, iPhonesTalk and iPhone Freak setting up categories to track “hacks” such as end-running AT&T activation to use the device as an iPod/Wi-Fi browser; expanding the availability of ring tones and wallpapers; adding voice recording; and pursuing the mother of all hacks--unlocking the iPhone to work on other carrier networks.

All of these hacks come with their own risks, from violating Apple and AT&T terms of service and warranties to taking a screwdriver to the precious (not to mention expensive) device and poking around with its innards.

Two of the latest hacks directly target telecom-related applications: VoIP and videoconferencing.

The VoIP solution isn’t so much a pure hack as a software release from Germany-based Shape Services called IM+ for Skype for iPhone, a Safari Web application—with special tweaks to take advantage of the iPhone’s touch-screen interface—that enables users to make and take Skype calls on the device. The software is currently free for a limited time for iPhone users.

Since The SHAPE application is browser-based, it can technically work on any phone. The company said it should work equally well over the iPhone’s available wi-fi or AT&T EDGE-based networks. Users can IM or talk with their Skype contacts via the Internet or use SkypeOut to reach landline phones.

As for adding videoconferencing to the iPhone, this falls much more in the realm of “hardcore hack.” A couple of enterprise developers used the recent C-4 developer conference and coding contest to implement the solution.

We won’t go into great detail here (you can read their first person story here and see a YouTube video of the device in action here. But among the hacks they successfully demonstrated: “tricking” the iPhone camera into capturing video and using something called a “Huckleberry mirror” to allow a user to view the iPhone screen while also sending their own image to the phone. To create the user interface, the developers used something called the iPhone ToolChain, which allows developers to write iPhone apps using the same development environment they use to write Mac apps.