Despite being the most popular VoIP service worldwide (nearly 350 million users at the time I am writing this), Skype is not very attractive to mobile users. This is because the amount of mobile devices on which Skype can be installed is very few. So here are ways how you can take Skype along with you in your pocket.
3 SkypephoneSkype promotes the 3 Skypephone, which is a quite restrictive phone developed in partnership with 3. The phone only has 3G connectivity and a few other features. It has nothing to do with the trendy mobile phones we know. So, there is nothing much you can do with the phone apart from running Skype. And oh, I forgot to mention the 3.2 MP camera. Furthermore, the phone is available only in the UK and a handful of other European countries.
PSPIf you have the latest Sony Playstation model (PSP 2000 series), you can make a free update and obtain Skype on it, and make free calls through your Wi-Fi or 3G connection.
Other Mobile PhonesHow about your Nokia or Sony Ericsson and so on? Well, Skype works only on some of these that are very expensive. So, you will be lucky only if you have the Nokia N800/N810 Internet Tablet (compare prices) or any mobile device running on Windows Mobile Professional or Standard operating system, e.g. Palm Treo, HTC Touch etc. Other (finally the great majority of) mobile phones and devices, as far as I know, simply do not support Skype. Better then try services like Yeigo or Fring.
Read more on Skype and Mobile Phones There.