The new 3 Skypephone is planned for a UK release on the 2nd of November '07, and other countries (including Ireland) after that. It will allow you to use the Skype client software that you would normally use on your computer on a 3G-enabled mobile phone. More details:
"3 Skypephone" - http://www.skype.com/intl/en/allfeatures/3skypephone/
This is likely to be a real winner for Skype users, as you can make free voice over IP calls to other Skype users from your mobile, and also use Skype instant messaging (although I have yet to find a mobile that I enjoyed typing a text message on, let alone a quick instant message conversation).
3 Ireland are already advertising the phones on their website:
"Skype on your 3Pay phone" - http://www.three.ie/handsets_new/skype/skype.htm
I will be tempted to get an upgrade when these arrive in Ireland, as it should cut down on my phone bill considerably.
Updated 2021 : note that the above post was originally published in 2007, but is left here for archival purposes. It seems the external links are now broken, so I have unlinked them.