A friend of mine suggested me to take a look to iSkoot for Skype: in small words, it's a Skype client for Blackberry, Nokia, and other mobile phone vendors.
From the iSkoot web site:
" iSkoot is free mobile software that delivers the rich features of Skype to your mobile handset.
We will be extending support to additional online and social networking communities soon!
With iSkoot software you can take advantage of Skype without being tethered to your PC.
iSkoot loads your Skype contact list right on your cell phone display screen, and with just a quick click of a button, you can call your contacts. "