Skype plans to begin offering a mobile VoIP client for iPhone through the iTunes App Store starting tomorrow. The New York times reports a BlackBerry version is due out in May.
The mobile clients will let users make free calls to other Skype users or low cost long distance and international calls to other phones. iPhone users will only be able to use Skype when connected to a WiFi hotspot, which prevents users from connecting to the AT&T network and skirting AT&T international fees by making calls over Skype.
In addition to making phone calls, the mobile client allows users to send instant messages, make conference calls, and snap profile photos using the iPhone's camera. You can find a series of screenshots of the iPhone app at Skype Journal.

Of course skpe has been on windows mobile forever

Skype has just opened the beta version of Skype 3.0 for Windows phones to public. It’s a free download from their website, and you some handy new features:
- Send files. - Free to send spreadsheets, photos, music and other files Skype-to-Skype.
- Send texts messages - Great value texts to mobiles abroad, and a great way to avoid roaming charges abroad if you text on Skype from a WiFi zone.

You can still download the full version of Skype 2.5, which gives you the standard free Skype-to-Skype calls and instant messaging, as well as calls to regular phones with Skype Credits.

To grab a copy of the new Skype 3.0 beta, click here. For the possibly-more-reliable Skype 2.5, go here.

Skype To Go is a service that lets you make cheap phone calls over Skype from a regular phone. Here's how it works. You sign up for a Skype To Go phone number that's linked to your Skype account. You can then dial that number from any phone to initiate a phone call to another phone at the same rates that you would pay if you were using Skype on your computer. In other words, if your mobile carrier charges $.99 per minute to call New Zealand and Skype charges $.02, you can just call a local number and pay the Skype rate.
Skype has been offering this service for a few years, but it was previously part of the Skype Pro plan. Now Skype is making Skype To Go available as a free service for all paying users. OK, I guess that means it's not technically free. But if you already have some credit in your account for making long distance phone calls, you can sign up for a Skype To Go number for no additional cost.