ISkoot
for S60

ISkoot is freeware that enables you to use Skype on your mobile phones and now the Blackberry. The software is still in BETA. ISkoot has an agreement with Skype to use their network. Now you can use your Skype account to make calls and send instant messages.
ISkoot uses your voice plan to connect to their server when you make and receive Skype calls so be careful if your not in North America , you might get long distance charges. Although Iskoot is still working on trying to improve their software the chat function works great and helps me get in touch with everyone in my office.